Di-and tripeptides of 3-(3,4-dihydroxyphenyl)-alanine

ABSTRACT

TRI- AND DI-PEPTIDES OF 3-(3,4-DIHYDROXYPHENYL)-ALANINE AND AN A-AMINO ACID OR DOPAMINE WHICH ARE USEFUL AS ANTI-PARKINSON AGENTS.

United States Patent O DI- AND TRIPEPTIDES F 3-(3,4-DIHYDROXY-PI-lENYL)-ALANINE Arthur Martin Felix, West Caldwell, NJ., assignor toHolimann-La Roche Inc., Nutley, NJ. No Drawing. Continuation-impart ofapplication Ser. No. 7 184,614, Sept. 28, 1971, which is acontinuation-in-part of application Ser. No. 85,713, Oct. 30, 1970, bothnow abandoned, This application Apr. 12, 1972, Ser. No.

Int. Cl. C07c 101/72, 103/52 US. Cl. 260-1125 57 Claims ABSTRACT OF THEDISCLOSURE Triand diepeptides of 3-(3,4-dihydroxyphenyl)-alanine and ana-amino acid or dopamine which are useful as anti-Parkinson agents.

CROSS REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of US. patent application Ser. No. 184,614, filedon Sept. 28, 1971, now abandoned which in turn is a continuation-in-partof US. patent application Ser. No. 85,713, filed on Oct. 30, 1970, nowabandoned.

SUMMARY OF THE INVENTION In accordance with this invention, it has beenfound that compounds selected from the formulae:

wherein R and R are f 3,803,120 Patented Apr. 9, 1974 or the source ofvariation in structure which differentiates one natural proteinoccurring a-amino acid from another; R and R are ice or the source ofvariation in structure which difierentiates one natural proteinoccurring u-amino acid from another; n is an integer of from 0 to 1; andR is lower alkyl;

and salts thereof are useful as anti-Parkinson agents.

When n in the compound of Formula II and Formula III is 0, the compoundsof Formulae II and III are dipeptides having the formula:

The products of Formulae I, II, III and IV above are prepared throughthe coupling of dopa which has the formula:

no nocmnH-oo 011 NH: (V)

with any one of dopa, dopamine, an u-amino acid of the formula:

wherein R is as above;

or a natural a-amino acid occurring in proteins.

DETAILED DESCRIPTION the preferred lower alkoxy moieties are includedmethoxy, ethoxy and propoxy.

The term aryl as used throughout the application includes mono-nucleararyl groups such as phenyl which can be substituted or unsubstituted inone or more positions with hydroxy, methylenedioxy, halogen, nitro,lower alkyl, lower alkoxy substituents and polynuclear aryl groups suchas naphthyl, anthryl, phenanthryl, azulyl, etc., which may besubstituted with one or more of the aforementioned groups.

The term aryl-lower alkoxycarbonyl, comprehends aryl-loweralkoxycarbonyl groups wherein the aryl and lower alkoxy moieties aredefined as above. The preferred aryl-lower alkoxycarbonyl groups arephenyl-lower alkoxycarbonyl with benzyloxycarbonyl being especiallypreferred.

The term alkoxycarbony as used herein includes lower alkoxycarbonylgroups wherein lower alkoxy is defined as above. Among the preferredlower alkoxycarbonyl groups are included methoxycarbonyl, ethoxycarbonyland isopropoxycarbonyl, with methoxycarbonyl being especially preferred.

The term lower alkanoyl includes alkanoyl radicals containing from 2 to6 carbon atoms such as acetyl, propionyl butyryl, etc. The termaryl-lower alkanoyl includes aryl lower alkanoyl radicals wherein aryland lower alkanoyl are defined as above. The preferred aryl loweralkanoyl radical is benzoyl.

As used in this specification (D) and (L) define the absoluteconfiguration about the asymmetric carbon of the stereoisomer of theformulat set forth.

The compounds of Formulae I, II, III and IV and their salts are usefulas anti-Parkinson agents. The compounds of Formulae, I, II, IH and IV aswell as their salts, are used in the form of conventional pharmaceuticalpreparations which contain said compounds in connection with conventonalpharmaceutical organic or inorganic materials suitable for internaladministration. The pharmaceutical compositions containing the compoundsof FOI- mulae I, II, III and IV as well as their salts can beadministered parenterally or orally. Dosages can be adjusted toindividual requirements, for example, these compounds can beadministered in dosages of from about 10 mg./kg. to about 70 trig/kg.p.o. per day. These dosages can be administered in a single dosage formor in divided dosage forms. The pharmaceutical compositions can containconventional organic or inorganic inert carrier materials such as water,gelatin, lactose, starch, magnesium stearate, talc, vegetable oils,gums, polyalkylene glycols, Vaseline and the like. The pharmaceuticalpreparations can be inconventional solid dosage forms such as tablets,drages, suppositories, capsules or in conventional liquid dosage formssuch as solutions, suspensions or emulsions. The pharmaceuticalcompositions can be submitted to conventional pharmaceutical expedientssuch as sterilization and/or can contain conventional pharmaceuticaladditives such as preservatives, stabilizing agents, wetting agents,emulsifying agents, salts for adjusting the osmotic pressure, buffers orthe like. They can also contain other therapeutically useful materials.Compositions can be formulated which contain from 1% to 99% of theactive ingredient of Formulae I, II, III and 1V and from 1% to 99% byweight of inert carrier materials.

The compounds of Formulae II, III and IV above, in the form of theirfree acids, are amphoteric in character. These compounds dissolve inwater as Well as in acids or in alkalies in which they form salts.

In accordance with this invention, the compounds of Formulae I, II, 'IIIand IV with their pharmaceutically acceptable salts exhibit theaforementioned beneficial therapeutic properties. The compounds ofFormulae II, III and IV form a pharmaceutically acceptable salt, withboth inorganic and organic pharmaceutically acceptable acids as well asbases. The compound of Formula 1 forms salts with pharmaceuticallyacceptable acids. Among the acids which the compounds of Formulae I, II,III and IV form pharmaceutically acceptable acid addition salts areincluded hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoricacid, citric acid, acetic acid, succinic acid, maleic acid,methanesulfonic acid, p-toluenesulfonic acid and the like. Such acidaddition salts are also within the scope of the invention.

The compounds of Formulae II, HI and IV also form pharmaceuticallyacceptable basic salts. Among the preferred pharmaceutically acceptablebasic salts of the compounds of Formulae 'I, II, HI and IV are includedalkali metal salts, such as sodium or potassium or the alkaline earthmetal salts such as calcium.

That the compounds of Formulae I, II, III and IV are eifectiveanti-Parkinson agents can be seen by the fact that compounds such as=L-3-(3,4-dihydroxyphenyl)-alanyl-L- 3 (3,4 dihydroxyphenyl)-alanine,glycyl-L-dopa; and L-tyrosyl-L-dopa have ED s less than 300 mgJkg. i.p.when administered to mice having catatonia induced by reserpine inaccordance with the procedure described by Chesare et al. in ArchivesInternationals, Pharmacodynamie et de Therapic 1-69, 26 (1967). On theother hand, the ED of L-dopa when administered by the same method was430 mgJg. i.p.

Dopa of Formula V and the a-amino acids utilized as starting materialscan be in their L-form, their D-form or in the form of a racemicmixture. Generally, it is preferred to utilize the L-form of thesestarting materials.

In the compounds of Formulae II, III and IV, R, R, R and R, can be theresidue of any natural a-arnino acid which occurs in proteins. Among thenatural a-amino acids that occur in proteins which can be utilized asthe starting materials in this inventon are the following:

Glycine Arginine Alanine Lysine Valine Hydroxylsine LeucinePhenylalanine Isoleucine Tyrosine Cysteine Asparagine Cystine GlutamineMethionine Proline Serine Hydroxyproline Threonine Histidine Asparticacid Tryptophan Glutamic acid Pyroglutamic acid In accordance with thisinvention are included compounds of the formula:

RivNH-CEC 0 OH wherein R is aralkoxycarbonyl; R is hydrogen .or

aralkoxycarbonyl;

and pharmaceutically acceptable salts thereof.

The compounds of Formula XX above, are useful in a manner similar to thecompounds of Formulae I, II, III and IV as anti-Parkinson agents.

In preparing compounds of Formula II where n is 0, i.e., a compound ofFormula II-A, an L-dopa derivative of the formula:

R -NH-CH-COOH (VII) wherein R is a conventional amino protecting groupwhich can be removed by hydrogenolysis or hydrolysis; and R is hydrogenor a group convertible thereto by hydrolysis or hydrogenolysis;

is coupled by means of a peptide coupling reaction with an a-amino acidderivative of the formula:

II NHz-CH-C-OR-r R" VIII wherem R is ORin to produce a compound of theformula:

$13.5 wherein R", R R and R are as above.

Any conventional means of peptide coupling can be utilized to react thecompound of the Formula VII with a compound of the Formula VIII toproduce a compound of the Formula IX. Among the conventional means forforming peptides which can be utilized in carrying out the process ofthis invention is to react the amine of Formula VIII with a compound ofFormula VII with the carboxylic acid group of Formula VII converted to areactive functional derivative thereof. Any conventional reactivederivative of an acid which will form a peptide bond with an amino groupcan be utilized in carrying out these reactions. Among the preferredreactive functional acid derivatives are halides, azides, anhydrides andactive esters such as N-hydroxy-succinimide ester, or para nitro phenylester, or activation by a C-N or a C-C multiple bond such asN,N-dialkylated carbodiimde. Any of the conditions conventional inreacting these acid functional derivatives with an amine to form apeptide linkage utilized in accordance with this invention.

A preferred method of carrying out this coupling is by reacting thecompound of Formula VII with a compound of Formula VIII in the presenceof a peptide coupling 6 with temperatures of from about l0 C. to about25 C. being preferred. Generally, it is preferred to start the reactionat a temperature of from about 10 C. and slowly allow the temperature ofthe reaction to rise to about 25 C.

In the compound of Formula VII, R can be any conventional aminoprotecting group which can be easily removed by hydrogenolysis andhydrolysis. Among the preferred amino protecting groups which can beutilized in accordance with this invention are aralkoxycarbonyl groupssuch as benzyloxycarbonyl as well as t-butyloxycarbonyl.

The compound of the Formula VII containing the amino protecting group isformed by reacting, in a conventional manner, the compound of theFormula V with an activated acid derivative of the protecting group suchas a halide of the protecting group to produce a compound of the for-NHR HO wherein R is as above.

Among the activated acid derivatives are included aralkoxycarbonylhalides and t-butyloxycanbonyl azides. Any of the conventional methodsof reacting an amine with an activated acid derivative to form aprotected amine can be utilized in carrying out this reaction.Particularly preferred for use in this invention is benzyloxycarbonylchloride.

'In the compound of Formula VII where R is a protective group removableby hydrogenolysis or hydrolysis, any conventional hydroxy protectinggroup can be utilized. Among the preferred protecting groups areincluded aralkoxycarbonyl groups such as benzyloxycarbonyl; loweralkanoyl, aralkanoyl such as benzoyl; alkyl groups and aryl lower alkylgroups. The protecting groups can be formed by reacting the compound ofFormula V-A with an aralkoxycarbonyl halide, lower alkanoyl halide,aralkanoyl halide, lower alkyl halide or an aryl lower alkyl halide. Anyconventional means of reacting a hydroxy group with a halide can beutilized in carrying out this reaction.

If it is desired to produce the compound of Formula VII whereis R and Rare aralkoxycarbonyl groups, the reaction is carried out wherein atleast 3 moles of the aralkoxycarbonyl halide is utilized per mole of thecompound of Formula V.

In preparing the compound of Formula VIII, an aamino acid of theformula:

wherein R is as above;

is esterified with a lower alkanol or an aryl lower alkanol. Thisesterilcation will also esterify free carboxyl groups that may bepresent in the residue of the a-amino acid designated by R such as arepresent in aspartic and glutamic acid. Any conventional method ofesterification can be utilized to carry out this reaction. Among thepreferred methods for esterifying the compound of the Formula X is bytreating the compound of Formula X with a lower alkanol or aryl loweralkanol in the presence of a dehydrating agent. Among the preferredalcohols for esterifying the a-amino acids are methyl alcohol, ethylalcohol, benzyl alcohol, isopropyl alcohol, etc. Among the preferreddehydrating agents are included thionyl chloride and sulfuric acid. 'Ifdesired, a solvent may be utilized in carrying out this esterificationreaction. Any conventional inert organic solvent can be utilized forthis purpose. Generally, it is preferred to carry out this reactionutilizing excess alcohol as a solvent medium. On the other hand,conventional organic solvents such as diethyl ether, tetrahydrofuran,etc., can be utilized. In carrying out this reaction, temperature andpressure are not critical and this reaction can be carried out at roomtemperature and atmospheric pressure. If desired, however, temperaturesas high as reflux temperatures and as low as l C. can be utilized.

In the case where R in the compound of Formula X does not contain anyamino groups, the compound produced by the esterification of theor-amino acid of Formula X can be utilized to react with the compound ofFormula VII to produce a compound of the Formula IX.

On the other hand, where R in the compound of Formula X contains a freeamino group and/or where it is desired to protect the free hydroxygroups or other functional groups which are present in the substituentR, then a compound of Formula X is converted to a compound of FormulaVIII by the following reaction scheme:

RlNH-CH C O OH N H R' (XII) l (0) ii NHr-C H-C-O R7 n (VIII) wherein R",R and R are as above; and R'" is 0 R: ME

(IBM:

or the source of variation in structure between natural proteinoccurring a-amino acid wherein all free amino groups are protected by agroup convertible thereto by hydrolysis or hydrogenolysis and the freehydroxy groups may be protected by protecting groups convertible theretoby hydrolysis or hydrogenolysis; and R R and R are as above.

The compound of Formula XI can be prepared from a compound of Formula Xby protecting the free amino and/or hydroxy or other functional groupsin the compound of Formula X as described in connection with theformation of the compound of Formula VII.

The compound of Formula XI is converted to the compound of Formula XIIby treating the compound of Formula XI with an agent selected from thegroup consisting of thionyl chloride, phosphorus oxychloride orphosphorus pentachloride. This reaction is generally carried out in aninert organic solvent at reflux temperature. Any conventional inertorganic solvent can be utilized. Generally, it

I is preferred to utilize solvents such as ethyl acetate or benzene.

The compound of Formula XII is converted to the compound of Formula VIIIby treating the compound of Formula XI I with an esterifying agent suchas a lower alkanol or an aryl lower alkanol. Any of the conditionsconventional in esterifying anhydrides can be utilized to convert thecompound of Formula XII to the compound of Formula VIII. This process ofesteri-fication provides a means for protecting all free carboxy groupsas well as all of the other free functional groups which may be presenton the amino acid residue.

The compound of Formula III above where n is 0, i.e.

the compound of Formula III-A above, is prepared by first reacting acompound of the formula:

1hr" (XIII) wherein R is as above; and R is ORio or the source ofvariation in structure between different natural protein occurringu-amino acid wherein all free amino and carboxyl groups are protected bya group convertible thereto by hydrolysis or hydrogenolysis and whereinthe free hydroxy group may be protected by a group convertible to freehydroxy by hydrolysis or hydrogenolysis; and R and R are as above; witha compound of the formula:

wherein R R R and R are as above.

The compound of the Formula XIV can be coupled with the compound of theFormula XIII in the same manner as disclosed in connection with thecoupling of the compound of the Formula VII and compound of the FormulaVIH.

The compound of Formula XIV can be produced from dopa by the same meansas described in connection with converting the vat-amino acid of FormulaX to the protected amino acid ester of Formula VIII.

In preparing the compound of Formula XIII, the free amino and hydroxygroups of the u-amino acid are protected by conventional protectinggroups which are convertible to free hydroxy or amino groups byhydrolysis or hydrogenolysis in the same manner described in connectionwith the formation of the compound of Formula VII. Any free carboxylgroup in R can be esteri-fied by treating the a-amino acid with analcohol and mineral acid such as hydrochloric acid. In this manneresterification will take place selectively on the carboxyl groups remotefrom the carbon atom. Any conventional method of forming an ester can beutilized in protecting the free carboxy moieties on the amino acidresidue.

In forming the compound of the Formula I, a compound of the formula:

R (VII) wherein R and R are as above;

is reacted with dopamine or a dopamine derivative of the formula:

(XVI) to produce a compound of the formula:

l Ha Ha wherein R R and R are as above.

(XVII) This coupling reaction is carried out by the same manner asdescribed in connection with the coupling of a compound of the FormulaVII with a compound of the Formula VHI to produce a compound of theFormula IX.

The compounds of Formulae IX, XV, XVII can be converted to a compound ofthe Formulae I, II-A and IIIA by hydrogenolysis and/or hydrolysisdepending upon the protecting groups as defined by R R R R R10 and R11.

In the compound of Formulae IX, XV, and XVII, where R isaralkoxycarbonyl, R is aryl lower alkyl, and R and R are aryl loweralkyl or aryl lower alkoxycarbonyl, these groups can be removed byeither hydrolysis or hydrogenolysis. The hydrogenolysis can be carriedout by catalytic hydrogenation. Any conventional means of catalytichydrogenation can be utilized in carrying out this hydrogenation step.Among the preferred methods of hydrogenation are included hydrogenatingin the presence of a palladium catalyst, preferably palladium on bariumsulfate in a solvent medium consisting of an alcohol and an organic acidsuch as a mixture of acetic acid and methanol. However, in accordancewith this invention, any conventional hydrogenation catalyst such aspalladium oxide, palladium chloride, etc., can be utilized. In carryingout this reaction, any conventional solvent can be utilized such as thesolvent hereinbefore set forth. Among the preferred solvents for use inthis reaction are included tetrahydrofuran, ethyl acetate, dioxane,diethyl ether, etc. Generally, this reaction is carried out attemperatures of from about 0 C. to 100 C., depending upon -the refluxand freezing temperature of the solvent.

In the case where all of the protecting groups on the compounds ofFormulae IX, XV and XVII are not removed by hydrogenolysis,hydrogenolysis of the compounds of Formulae IX, XV and XVII producecompounds having the formula:

wherein R is hydrogen or a group convertible thereto by hydrolysis; R islower alkyl; R-,' is hydrogen or lower alkyl; R and R are hydrogen or agroup convertible thereto by hydrolysis; R is or the source of variationin structure between different natural protein occurring a-amino acidswherein all hydroxy, carboxy and amino groups are free or protected by agroup convertible thereto by hydrolysis, with the proviso that one of RR26, R and R is other than hydrogen;

wherein R is as above; R is hydrogen or lower alkyl; R is hydrogen or agroup convertible thereto by bydrolysis; R is or the source of variationin structure between different natural protein occurring OL'HIIIIIIOacids wherein all amino, carboxy and hydroxy groups are free orprotected by a group removable by hydrolysis; R is lower alkyl with theproviso that one of R50, R and R is other than hydrogen;

CIH: CH;

0 Rar 0R3:

0R3: (XVII-A) wherein R is as above; R and R are hydrogen or a groupconvertible thereto by hydrolysis with one of R R and R being other thanhydrogen.

The compounds of Formulae lX-A, XV-A and XVII- A falling outside thescope of Formulae IX, XV and XVII are those which contain one free aminoand/or carboxy group.

The compounds of Formulae IX, XV and XVII can be hydrolyzed by acidtreatment. If desired, this acid treatment can be carried out before orafter the hydrogenation procedure set forth above. In carrying out thisacid hydrolysis, any strong mineral acid can be utilized. Among thepreferred strong mineral acids are included sulfuric acid, hydrochloricacid, hydrobromic acid and hydroiodic acid, the preferred acids beinghydrobromic acid and hydroiodic acid. When a strong mineral acid isutilized, the reaction is generally carried out in an organic solventsuch as acetic acid, dioxane or acetone at temperatures of 25 to 100 C.A means of hydrolyzing these groups in the compounds of Formulae IX, XVand XVII is by treatment with a Lewis acid such as borontrifluoride etc.This acid treatment is carried out in an ether or halogenatedhydrocarbon solvent, preferably methylene chloride and/or an ethylether. In carrying out this reaction, temperatures of from 78 C. to 35C. are utilized. This acid treatment of the compound of Formula IX, XVand XVII will also hydrolyze and remove aryl lower alkyl or alkyl groupswhich may be utilized to protect the hydroxy groups, aryl lower alkyl oralkyl groups which may be utilized to protect the carboxy groups andt-butoxy carbonyl which may be utilized to protect the amino groups.

When R" and R in the compounds of Formula IX, and Formula XV are formedfrom natural a-amino acids containing an additional free amino orcarboxy radical which radicals are protected by a protecting group thatcan be hydrolyzed or hydrogenated to form the free amino or carboxyradical, these protecting groups can be removed by hydrogenation orhydrolysis, depending upon the group, in the manner given before. In thecase where the free carboxyl group is esterified with an alkyl radicalthese esters can be hydrolyzed in the aforementioned manner. In the casewhere the acid residue contains an additional free amino group such aslysine, and the amino group is protected by an aralkoxycarbonyl radicalsuch as carbobenzoxy, this radical can be removed by hydrogenation orhydrolysis in the aforementioned manner. Furthermore, where the aminoacid residues which contain a free bydroxy group such as tyrosine whichis protected by an alkyl, alkanoyl or aralkanoyl radical, theseprotected radicals can be removed to regenerate the free hydroxy groupby hydrolysis. On the other hand, where the free hydroxy groups areprotected by an aralkoxy-carbonyl or aralkyl, these protective groupscan be removed to regenerate the free hydroxy group by hydrogenation orhydrolysis in the manner given above.

In accordance with this invention, it has been found that when R and Rin the compounds of Formulae VII, XIV and XVI are aralkoxycarbonyl,lower alkyl, t-butoxycarbonyl, aryl lower alkyl, lower alkanoyl or aryllower alkanoyl, coupling provides an efiicient means for producingcompounds of Formulae IX, XV and XVII. By providing these substituentson the hydroxy groups of the phenyl moiety of the compounds of FormulaeVII, XIV, and XVI, the compounds of Formulae IX, XV, and XVII may beobtained with a high degree of purity.

The compound of Formula II above wherein n is 1 has the formula:

! H: R R

The compound of Formula II-B is prepared by first condensing compoundsof the formula:v

(II-B (XXV) and l B 7 R27 (XXVI) wherein R is 10 CHz -0Ra, CH; 5 g

or the source of variation in structure between natural proteinoccurring a-amino acids wherein all free amino or carboxy groups areprotected by a group convertible thereto by hyrogenolysis or hydrolysis,and any free hydroxy group may be protected by a group convertiblethereto by hydrolysis or hydrogenolysis; x and y are integers of from 0to 1 with the sum of x and y being equal to l; R, R R R and R are asabove; R is -OH or a reactive functional acid derivative, and R is OH,aryl lower alkoxy or lower alkoxy with the proviso that one of R and Ris other than OH;

to produce a compound of the formula:

wherein R R R and R are as above;

(XXV II) can be utilized. Among the reactive functional acid derivativesare the reactive functional derivatives set forth in connection with thecondensation reaction of a compound of the Formula VII with a compoundof the Formula VIII. The preferred reactive functional derivatives arethe active esters such as para-nitro phenyl ester. Where R is a reactivefunctional acid derivative and R is hy droxy, alkoxy or aryl loweralkoxy, the condensation reaction to form the compound of Formula XXVIIcan be carried out utilizing any of the conventional methods forreacting an organic reactive functional derivative of an organic acidwith an amine to form an amide linkage. This reaction may be carried outin the presence of a tertiary amine base. However, this reaction can becarried out simply in an inert organic solvent Without the presence of abase. The presence of a tertiary amine base improves the rate of thiscoupling reaction. Any conventional tertiary amine base can be utilized.Among the preferred tertiary amines are included triethyl amine,pyridine, trimethyl amine, N-ethyl-N,N-dimethyl amine, N-methylpiperidine, etc. In carrying out this reaction, any conventional inertorganic solvent can be utilized as the reaction medium. Among thepreferred solvents are included ethyl acetate, tetrahydrofuran anddimethyl formarnide. Furthermore, in carrying out this reactiontemperatures of from 10 C. to 50 C. are generally utilized, withtemperatures of from 10 C. to 30 C. being preferred.

Where R is a hydroxy group and R is lower alkoxy or aryl lower alkoxygroup, this reaction can be carried out in the presence of a peptidecoupling agent utilizing the conditions described in connection with thereaction of the compound of the Formula VII with a compound of theFormula VIII.

The compound of the Formula XXVII can be converted to the compound ofthe Formula II by hydrogenolysis or hydrolysis or both hydrolysis andhydrogenolysis depending upon the protecting groups as defined by R R RR" and R This reaction can be carried out in the same manner asdescribed in connection with the conversion of the compound of theFormulae IX, XV and XVII to their respective dipeptides.

In the case where all the protective groups of the compound of FormulaXXVII are not removed by hydro genolysis, hydrogenolysis of the compoundof the Formula XXVII produces a compound having the formula:

wherein R is The compound of Formula XXVIII can be converted to thecompound of Formula II-B by hydrolysis as described hereinbefore.

The compound of Formula 'III wherein n is 1 has the formula:

wherein R and R are as above.

The compound Formula III-B is prepared by condensing compounds of theformula:

x Xxx (III-B) and R; (XXXI) wherein R R", R R R R and x and y are aabove;

to produce a compound of the formula:

' u I? ll RsNHCH-CNH-CH-C-NH-OH-CRas R!!! I! H,

wherein R", R R R and R are as above;

and then subjecting a compound of the Formula XXII to hydrolysis,hydrogenolysis or both hydrolysis and hydrogenolysis to produce thecompound of Formula III-B.

The condensation of the compound of the Formula XXX with the compound ofFormula XXXI to produce a compound of the Formula XXXII is carried outas described in connection with the formation of a compound of theFormula XXVI'I. Hydrogenolysis and/or hydrolysis of the compound ofFormula XXXII to produce a compound of the Formula III-B is carried outin the manner described in connection with the conversion of compoundsof the Formula XXVII to a compound of the Formula II-B.

When hydrogenolysis of the compound of Formula XXXII does not remove allof the protecting groups, the compound produced thereby has the formula:

(XXXII) ORI O R (XXXIII) wherein R R R R and R are as above, with theproviso that the compound contains at least one of the hydroxy, carboxyor amino groups protected by a group removable by hydrolysis.

The compound of Formula XXXIII can be converted to the compound ofFormula III-B by hydrolysis as described hereinbefore.

The compound of Formula IV is prepared by first condensing compounds ofthe formula:

wherein R R R R R R x and y are as above;

by the procedure given in connection with the condensation of compoundsof the Formula XXV with compounds '15 of the Formula XXVI, to produce acompound of the formula:

wherein R R R R are as above; and R is The compound of Formula XLII canbe converted to the compound of Formula IV by hydrogenolysis orhydrolysis or by both hydrogenolysis or hydrolysis in the mannerdescribed hereinbefore.

If, upon hydrogenolysis all of the protecting groups are not removedfrom the compound of Formula XLII, the resulting compound has theformula:

(XLII) 25" l H: R2!

0Rzu

I 0R2 (XLIII) wherein R R R and R are as above; R is or the source ofvariation in structure between different natural protein occurringa-amino acids where all amino, carboxy, and hydroxy are free orprotected by a group removable by hydrolysis, and R is as above with theproviso that the compound contains at least one of the hydroxy, carboxyor amino groups protected by a group removable by hydrolysis.

The compound of Formula XLIII can be converted to the compound ofFormula IV by hydrolysis in the manner described hereinbefore.

The invention is fully illustrated in the following examples. Alltemperatures are in degrees centigrade. The ether utilized in theseexamples is diethyl ether. The petroleum ether utilized had a boilingrange of from 37 to 63 C.

EXAMPLE 1 L-3-(3,4dihydroxyphenyl)alanine benzyl ester hydrochloride Amixture of L-dopa (10.0 g., 0.05 mole) and benzyl alcohol (250 ml.) wasplaced in a 1 l. round-bottomed flask fitted with a reflux condenser,magnetic stirring as sembly and immersed in an ice bath. Thionylchloride (50 ml.) was added dropwise with stirring over a 30 minuteperiod. The ice bath was removed and the solution was heated to 100 for6 hours. At the end of this time the solution was treated with diethylether and allowed to stand at 0 C. There was obtainedL-3-(3,4-dihydroxyphenyl)alanine benzyl ester hydrochloride as acrystalline product. Crystallization from ethanol diethyl ether gaveproduct, M.P. 174-178 C.

This hydrochloride was converted to L-3-(3,4-dihydroxyphenyl)alaninebenzyl ester by treatment with saturated aqueous sodium bicarbonateextraction into ethyl acetate and evaporation to dryness.

EXAMPLE 2 N-benzyloxycarbonyl-L-3- (3,4-dihydroxyphenyl alanine Into a 1l. 3-necked round bottomed flask equipped with 2 dropping flasks,mechanical stirrer and immersed in an ice-salt bath was placed 55 ml. of1.0 M NaOH (0.055 mole) and water (300 ml.) added. Nitrogen was bubbledthrough the system and L-dopa (1195 g., 0.06 mole) was added.Carbobenzoxychloride (9.35 g., 0.055

' mole) in diethyl ether (55 ml.) and 55 ml. of 1.0 M

NaOH (0.055 mole) were simultaneously added dropwise to the rapidlystirring mixture over a 30 minute period.

The reaction mixture stirred for 4 hours at 5 C. It was transferred to aseparatory funnel and rapidly extracted 3 times with diethyl ether. Theaqueous layer was acidified with aqueous 2 M HCl to pH 2 and extracted 3times with diethyl ether. This ether layer was dried over magnesiumsulfate, filtered and evaporated to dryness. There was obtainedN-benzyloxycarbonyl-L- 3-(3,4-dihydroxyphenyl)alanine as a whiteamorphous solid.

EXAMPLE 3 N-benzyloxycarbonyl-L-Zi- (3 ,4-dihydroxyphen yl) alanyl-L-3-(3,4-dihydroxyphenyl)alanine benzyl ether Into a 250 m1.round-bottomed flask equipped with a magnetic stirring assembly andimmersed in an ice-salt bath was placedN-benzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)alanine (1.7 g., 5 mmole)in tetrahydrofuran (75 ml.). L-3-(3,4-dihydroxyphenyl)alanine benzylester (1.5 g., 5 mmole) was added. The clear solution was treated withdicyclohexylcarbodiimide (1.05 g., 5 mmole) and the reaction mixturestirred 2 hours at -5. It was warmed to room temperature (precipitationof urea commenced) and stirred at room temperature overnight. It wasfiltered, evaporated to dryness, taken up in ethyl acetate and extractedthree times each in turn with saturated aqueous. sodium bicarbonatesaturated brine and hydrochloric acid, dried over magnesium sulfate,filtered and evaporated to dryness. There was obtained N-ben-Zyloxycar-bonyl L 3 (3,4-dihydroxyphenyl)alanyl-L-3-(3,4-dihydroxyphenyl)alanine benzyl ester as an olfwhite amorphoussolid.

EXAMPLE 4 L-3 (3,4-dihydroxyphenyl a1anyl-L-3- (3 ,4- dihydroxyphenyl)alanine N-benzyloxycarbonyl L 3 (3,4-dihydroxyphenyl) alanyl-L-3-(3,4dihydroxyphenyl)alanine benzyl ester (3.0 g., 5 mmole) was placed in a500 ml. pressure bottle. Methanol (75 ml.), glacial acetic acid (5 ml.)and 5 g. of a mixture containing 5% by weight palladium and by weightbarium sulfate, were added and the reaction mixture was hydrogenated at48 p.s.i. on the Parr hydrogenator for 4 hours. It was filtered,evaporated to dryness. The residue was taken up in water and evaporatedto dryness. This procedure of evaporation from water was repeated 2 moretimes. The residue was taken up in'water, filtered to remove someinsoluble material and lyophilized. The resultant product was taken upin water (20 ml.), filtered and lyophilized. This procedure was repeatedonce more. There was obtained L-3-(3,4-dihydroxyphenyl)alanyl-L-3-(3,4dihydroxyphenyl)alanine asa white amorphous solid, M.P. 1-68-l71 C..which resolidifies and melts at 283-286 C. (dec.)

1 7 EXAMPLE 5 N,0,0-tris-benzyloxycarbonyl L 3 (3,4 dihydroxyphenyl)alanine Into a 3 liter 3-necked round-bottomed fi'ask fitted withmechanical stirred, nitrogen inlet tube and immersed in an ice-salt bath.was placed 240 ml. of 1 M aqueous NoOH (0.24 mole) and 500 ml. ofwater. Nitrogen was passed through the system for 15 minutes and L-dopa(47.4 g. 0.24 mole) added. To this cold stirring solution was addeddropwise simultaneously 800 ml. of 1.0 M aqueous NaOH (0.80 mole) andbenzyloxycarbonyl chloride (136.5 g., 0.80 mole) in 800 ml. diethylether. The addition required 30 minutes. The reaction mixture stirred atC. for 2 hours and at 25 C. overnight. The reaction mixture was filteredand the precipitate was washed with diethyl ether, titurated with 1Naqueous citric acid and extracted into diethyl ether (3x 250 ml.). Thiscombined ethereal solution *was dried over MgSO filtered and evaporatedto dryness. The residue was triturated with petroleum ether and 'driedin vacuo. There was obtained N,0,0'-tris-benzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)alanine as an amorphous tan solid (hygroscopicEXAMPLE 6 N,0,0'-tris-benzyloxycarbonyl L 3 (3,4dihydroxyphenyl)alanyl-L-3-(3,4-dihydroxyphenyl)alanine benzyl esterInto each of two l-liter 3-necked round-bottomed flasks equipped with amechanical stirrer and immersed in an ice-salt bath was placedN,0,0'-tris-benzyloxycarbonyl-L-3-(3,4 dihydroxyphenyl)alanine (16.0 g.each; 32.0 g., 0.0534 mole total) and L-3-(3,4-dihydroxyphenyl)alaninebenzyl ester (7.67 g. each; 1534 g., 0.0534 mole total) in 450 ml. ofdry tetrahydrofuran. The reaction' mixtures were cooled anddicyclohexylcarbodiimide (5.5 g. each; 11.0 g., 0.0534 mole total) in 30ml. of tetrahydrofuran, dried by passage through a column of alumina,was added to each solution. 'The reaction mixtures stirred at 0 for 2hours and at 25 overnight. The reaction mixtures were filtered and thefiltrates combined and evaporated to dryness. The residual oil was takenup in 1.2 liter of diethyl ether, filtered and the filtrate extractedwith saturated NaHCO (3 X 250 ml.), citric acid (3X 150 ml.) andsaturated brine (3X 150 ml.). The ethereal layer was dried over MgSOfiltered and evaporated to dryness. The residual oil was taken up in aminimum amount of chloroform, filtered through a pad of silica gel,eluted with chloroform, hexane (1:1 parts by volume). The eluate wasevaporated to dryness to yield N,0,0-tris-benzyloxycarbonyl-L-3-(3,4dihydroxyphenyl)alanyl-L-3-(3,4-dihydroxyphenyl)alanine benzyl ester asan amorphous white solid.

EXAMPLE 7 L-3-(3,4-dihydroxyphenyl) alanyl-L-3- (3,4-dihydroxyphenyl)alanine Into a 500 ml. pressure bottle was" placedN,0,0'-trisbenzyloxycarbonyl L 3 (3,4dihydroxyphenyl)alanyl-L-3-(3,4-dihydroxyphenyl)alanine benzyl ester (30.3 g., 34.9 mmole).Methanol (200 ml.), acetic acid (glacial, 5.0 ml.) and g. of a mixturecontaining 5% by weight palladium and 95% by weight barium sulfate wereadded and the mixture hydrogenated at 45.5 psi. for 17 hours. It wasfiltered through celite and evaporated to dryness. The residue was takenup in water (450 ml.) and extracted with ethyl acetate (3 X 300 ml.) anddiethyl ether (200 ml.). The aqueous solution was evaporated to dryness,taken up in water and re-evaporated to dryness and finally lyophilizedfrom water. There was obtained L-3- (3,4 dihydroxyphenyl)alanyl L 3 (3,4dihydroxyphenyl)alanine as a white amorphous solid, M.P. 151- 18 EXAMPLE8 N-u-benzyloxycarbonyl-L-3-(3,4-dibenzyloxycarbonyloxyphenyl) -N- (3,4-dimethoxyphenethyl) alaninamide Into a 250 ml. l-neckedround-bottomed flask immersed in an ice-salt bath was placedN,0,0'-tris-benzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)alanine g., 0.02mole) in dry tetrahydrofuran (50 cc.). Homoveratrylamine (3.62 g., 9.92mole) was added and the solution stirred at 5 C. for 15 minutes.

Dicyclohexylcarbodiimide (4.13 g., 9.92 mole) was added and stirringcontinued at 5 C. for 2 hours and 25 C. for 2 days. The reaction mixturewas filtered, evaporated to dryness, taken up in chloroform (75 cc.) andextracted with saturated aqueous NaHCO' (3X 50 cc.), saturated KCl (3X50 cc.) and 2 M aqueous citric acid (3X 50 cc.). The chloroform layerwas dried over MgSO filtered and evaporated to dryness. The product wascrystallized from methanol. There was obtained N-abenzyloxycarbonyl L 3(3,4 dibenzyloxycarbonyloxyphenyl)-N-(3,4-dimethoxyphenethyl)alaninamideas a white amorphous solid, M.P. 135.5138.5 C.

EXAMPLE 9 L-3-(3,4-dihydroxyphenyl)-N-(3,4-dimethoxyphenethyl)alaninamide acetate Into a 500 ml. pressure bottle was placedN-a-benzyloxycarbonyl-L-3-(3,4dibenzyloxycarbonyloxyphenyl)-N-(3,4-dimethoxyphenethyl) alaninamide(16.1 g., 0.0211 mole) in a mixture of methanol:tetrahydrofuran: aceticacid (100:50210 parts by volume) and a mixture containing 5% by weightpalladium and by weight barium sulfate (5.0 g.). The reaction mixturewas hydrogenated at 45 p.s.i. for 17 hours, filtered through Celite andevaporated to dryness. The residue was evaporated from water 4 times,taken up in water, filtered through charcoal and lyophilized. There wasobtained L-3-(3,4- dihydroxyphenyl) N (3,4 dimethoxyphenyl) alaninamideacetate as an amorphous white solid, M.P. decomposition from 74 C.

EXAMPLE 10 L-3- (3,4-dihydroxyphenyl)-N- (3,4-dihydroxyphenethyl)alaninamide hydrobromide Into a 500 ml. l-necked round-bottomed flaskequipped with a magnetic .stirring assembly and drying tube was placed L3 (3,4-dihydroxyphenyl)-N-(3,4-dimethoxy phenethyl) alaninamide acetate(4.2 g., 0.01 mole) in methylene chloride cc.). A solution of borontribromide (12.5 g., 0.05 mole, 5 equivalents) in methylene chloride wasadded portionwise and the reaction mixture stirred at 25 C. overnight.Methanol (75 cc.) added and the solution evaporated to dryness. Thisevaporation from methanol was repeated two more times and was followedby evaporation from water (50 cc.). The residue was taken up in water(50 cc.), extracted with diethyl ether (3X 25 cc.) and the aqueous layerevaporated to dryness. The residue was taken up in water, filteredthrough charcoal and lyophilized. There was obtained L-3-(3,4-dihydroxyphenyl)-N-(3,4 dihydroxyphenethyl) alaninamide hydrobromide asan amorphous off-white solid, M.P. decomposition from 104 C.

EXAMPLE 11 Tablets are manufactured utilizing the following composition:

The active substance is mixed with the lactose and the corn starch, and,after the addition of a solution of polyvinylpyrrolidone in 40 ml. ofethanol, granulated. The granulate is dried at 30 C., mixed with talcumand pressed to tablets.

Individual weight of one tablet 200 Active substance content of onetablet 100 EXAMPLE 12 Gelatin capsules are manufactured utilizing thefollowing composition:

The ingredients are homogeneously mixed and filled into interlockinggelatin capsules via a capsule filling machine.

Individual weight of one capsule 150 Active substance content of onecapsule 50 EXAMPLE 13 L-3-(3,4-dihydroxyphenyl)alanine ethyl ester Amixture of L-dopa g., 0.025 mole) and ethanol (150 ml.) was placed in a500 ml. round-bottomed flask fitted with a reflux condenser, magneticstirring assembly and immersed in an ice bath. Thionyl chloride (25 ml.)was added dropwise with stirring over a 30 minute period. The ice bathwas removed and the solution was heated to reflux for 4 hours. At theend of this time the solution was evaporated was evaporated to dryness.It was triturated with ether to give a solid product and crystallizedfrom ethanol-ether.

, This ethyl ester hydrochloride was converted to the free base, i.e.,L-3-(3,4-dihydroxyphenyDa1anine ethyl ester by treatment with saturatedaqueous sodium bicarbonate and extraction into ethyl acetate followed byevaporating to dryness.

EXAMPLE 14 N-benzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)alanine ethylester Into a 250 ml. l-necked round-bottomed flask immersed inan'ice-salt bath was placed L-3-(3,4-dihydroxyphenyl)aianine ethyl esterhydrochloride (3.5 g., 13.4 mmole) in 134 ml. of 0.1 -M NaOH (13.4mmole). Benzyloxycarbonyl chloride (2.06 g., 12.1 mmole) in ether (25cc.) and 12.1 ml. of 1.0M NaOH (12.1 mmole) were added simultaneouslywith rapid stirring. Stirring continued at --5 for 1 hour and at 25 for1 hour. The reaction mixture was acidified with l M HCl and extractedwith ether. The ether layer was extracted with saturated aqueous NaHCOsaturated aqueous KCl and 1 M HCl, dried over MgSO filtered andevaporated to dryness to give 3.45 g. ofN-benzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)alanine ethyl ester as acolorless oil.

EXAMPLE l5 N,0,0'-tris-benzyloxycarbonyl-I ,-3-(3,4-dihydroxyphenyl)alanyl-L-3-( 3,4-dihydroxyphenyl) alanine ethyl ester hours and 25overnight. It was filtered, evaporated to dryness, taken up in ethylether, filtered and extracted three times each with saturated NaHCO,,, 2M citric acid and saturated brine. The ethereal layer was dried overMgSO filtered and evaporated to dryness and gave N,0,0'tris-benzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)alanyl-L-3-(3,4-dihydroxyphenyl)alanine ethyl ester.

EXAMPLE 1 6 L-3-(3,4-dihydroxyphenyl)alanyl L 3(3,4-dihydroxyphenyl)alanine. Mineral acid hydrolysis ofN,0,0'-trisbenzyloxycarbonyl-L3-(3,4 dihydroxyphenyl)alanyl-L-3-(3,4-dihydroxyphenyl) alanine ethyl ester A suspension ofN,0,0-tris-benzyloxycarbonyl-L-ia- (3,4dihydroxyphenyl)alanyl-L-3-(3,4-dihydroxyphenyl) alanine ethyl ester(4.04 g., 0.005 mole) in 100 ml. of 12 M HCl was heated to 37 forminutes. At the end of that time, the reaction mixture was extractedwith ether and the aqueous solution evaporated to dryness. The residuewas taken up in water and re-evaporated to dryness. This procedure wasrepeated two more times and L3- (3,4 dihydroxyphenyl)alanyl-L-3-(3,4dihydroxyphenyl)alanine was finally crystallized from a small volume ofwater.

EXAMPLE 17 N-benzyloxycarbonyl-L-3-(3,4-dibenzyloxyphenyl)alanine Nbenzyloxycarbonyl-L-3-(3,4 dihydroxyphenyl)alanine ethyl, ester (3.59g., 0.01 mole), benzyl bromide (5.13 g., 0.03 mole), potassium carbonate(5.53 g., 0.04 mole) and acetone (50 ml.) were heated to reflux for 16hours. The reaction mixture was evaporated to dryness, taken up in theethyl acetate and extracted with water. The ethyl acetate layer wasdried over MgSO filtered and evaporated to dryness. The product wastaken up in 10 ml. of 1 M sodium hydroxide (.01 mole), dioxane (20 ml.)and water (10 ml.) added and the reaction mixture stirred at 25 for 14hours. Water (100 ml.) added and extracted with diethyl ether threetimes. The aque ous layer was acidified with cold 1 M H 80 and extractedthree times with ethyl acetate. The ethyl acetate layer was washed withwater, dried over MgSO filtered and evaporated to dryness to giveN-benzyloxycarbonyl- L-3- (3 ,4-dibenzyloxyphenyl) alanine.

EXAMPLE 18 N benzyloxycarbonyl L 3 (3,4 dibenzyloxyphenyl)alanyl L 3(3,4 dihydroxyphenyl)alanine benzyl ester Into a 1 liter 3-neckedround-bottomed flask equipped with a mechanical stirrer and imersed inan ice-salt bath was placedN-benzyloxycarbonyl-L-3-(3,4-dibenzyloxyphenyl)alanine (5.12 g., 0.01mole) and L-3-(3,4-'dihydroxyphenyl)alanine benzyl ester (2.87 g., 0.01mole) in 200 ml. of dry tetrahydrofuran. To the reaction mixture wasadded 2.06 grams (0.01 mole) of dicyclohexylcarbodiimide. The reactionmixture stirred at 0 for 2 hours and at 25 overnight, filtered,evaporated to dryness, taken up in ethyl ether, filtered and extractedthree times each with saturated NaHCO 2 M citric acid and saturatedbrine. The ethereal layer was evaporated to dryness and gaveN-benzyloxycarbonyl-L-3-(3,4-dibenzyloxy phenyl) alanyl-L-3-3,4-dihydroxyphenyl) alanine benzyl ester.

EXAMPLE 19 L 3 (3,4 dihydroxyphenyl)alanyl L 3 (3,4dihydroxyphenyl)alanine. Hydrogenation of N-benzyloxycarbonyl L 3 (3,4dibenzyloxyphenyl)alanyl- L-3-(3,4-dihydroxyphenyl)alanine benzyl esterInto a 250 ml. pressure bottle was placed N-benzyloxycarbonyl L 3 (3,4dibenzyloxyphenyl)alanyl L 3- (3,4-dihydroxyphenyl)alanine benzyl ester(3.91 g., 0.005 mole). Methanol (50 mL), acetic acid (glacial, 1 ml.)and 1 g. of a mixture containing 5% by weight palladium and by weightbarium sulfate were added and the mixture hydrogenated at 40 p.s.i. for18 hours. It was filtered through Celite, evaporated to dryness, takenup in water and extracted 3 times with ethyl acetate. The aqueoussolution was evaporated to dryness, taken upin water, re-evaporated todryness and finally crystallized from a small volume of water to produceL-3-(3,4-'dihydroxyphenyl)alanyl L 3 (3,4 dihydroxyphenyl) alanine.

EXAMPLE 20 L 3 (3,4 dihydroxyphenyl)alanyl L 3 (3,4 di

hydroxyphenyl)alanine. Boron tribrornide cleavage of N benzyloxycarbonylL 3 (3,4 dibenzyloxyphenyl)alanyl L 3 (3,4 dihydroxyphenyl)alaninebenzyl ester Into a 250 ml. l-necked round-bottom flask was placedN-benzyloxycarbonyl-L-3-(3,4-dibenzyloxyphenyl) alanyl-L 3(3,4-dihydroxyphenyl)alanine benzyl ester (782 mg., 1.0 mmole) in 50 cc.of methylene chloride. Boron tribromide (2.50 g., 10 mmole, 10equivalents) was added dropwise with stirring and continued to stir at25 for 14 hours. Water (50 ml.) 'addedand the layers separated. Theaqueous layer was retained, washed 3 times with ethyl ether, andevaporated to dryness. The residue was taken up in water,re-eva'p'orated to dryness and finally crystallized from a small volumeof water to produceL-3-(3,4-dihydroxyphenyl)alanyl-L-3-(3,4-dihydroxyphenyl) alanine.

EXAMPLE 21 N,O-dicarbobenzoxy-L-tyrosine L-tyrosine (57.5 g., 0.317mole) Was dissolved in 300 ml. of 2 N NaOH at Carbobenzoxy chloride (140g.) and 4 N NaOH solution (400 ml.) were added simultaneously to thestirred solution over a period of 60 minutes. The solution was washedthree times with ether and then acidified to pH 2 with 4 N HCl, thewhite solid mass that formed was taken into 1 liter of methylenechloride and washed in turn with saturated sodium chloride solution andwater. Drying over sodium sulfate and evaporating off the solvent gave acrystalline residue. Recrystallization from boiling carbon tetrachloridegave N,O-dicarbobeuzoxy-L-tyrosine, melting at 123-126" C.

EXAMPLE 22 N, 0-dicarboboenzoxy-3-methoxy-L-tyrosine Into a 500 m1.3-necked round-bottomed flask fitted with a mechanical stirrer andimmersed in an ice-salt bath was placed 23.7 ml. of 1 N NaOH (23.7 mm.)and water (50 ml.). A stream of nitrogen was passed through the coldstirring solution for 20 minutes and 3-methoxy-L- tyrosine (5.0 g., 23.7mm.) added. This was followed by simultaneous addition of 1 M NaOH (52.2ml., 52.2 mm.) and carbobenzoxy chloride (8.9 g., 52.2 mm.) in ether (50ml) with vigorous stirring over a 30 minute period. Stirring continuedat for 1.5 hours and at 25 for 1 hour. It was transferred to aseparatory funnel, washed with ether (3x 200 ml.) and the aqueous layeracidified with saturated citric acid and extracted into ether (3X 200ml.). This latter ethereal solution was washed with water (4X 40 ml.),dried over magnesium sulfate, filtered and evaporated to dryness. Theresidue was tn'turated with petroleum ether. Filtration 'aifordedN,O-dicarbobenzoxy 3 methoxy L tyrosine as white prisms, M.P. 126-l29 C.

EXAMPLE 23 N,0,0-tricarbobenzoxy-D-dopa EXAMPLE 24O-carbobenzoxy-L-tyrosine benzyl ester hydrochloride Nine grams (0.022mole) of N,O -dicarbobenzoxy-L- tyrosine was suspended in 500 ml. ethylether, and reacted EXAMPLE 25 3-methoxy-O-carbobenzoxy-L-tyrosine benzylester hydrochloride Into a 1 liter S-necked round-bottomed flask wasplaced N,O-dicarbobenzoxy-3-methoxy-L-tyrosine (6.6 g., 13.8 mm.) in drychloroform (200 ml.). Nitrogen was flushed through the system andphosphorus pentachloride (2.88 g., 13.8 mm.) added with stirring over a1 hour period. The reaction mixture was filtered and the filtrateevaporated to dryness. The residue was taken up in dry chloroform (150ml.) and evaporated to dryness. This process was repeated two more timesto give the N-earboxyanhydride of 3-methoxy-O-carbobenzoxy-L-tyrosine asa colorless oil.

The oil was placed in a 1 liter round-bottomed flask fitted with adrying tube and magnetic stirring assembly and treated with a freshlyprepared solution of 0.7 M HCl in benzyl alcohol (150 ml.). The reactionmixture was stirred at C. for 35 minutes, cooled to 25 C. and treatedwith 450 ml. of dry diethyl ether and 900 ml. of petroleum ether. Therewas obtained a product which was recrystallized fromethanol-ether-petroleum ether to give3-methoxy-O-carbobenzoxy-L-tyrosine benzyl ester hydrochloride as whitecr'ystals, M.P. 7680 C.

EXAMPLE 26 General method .for the coupling of N-carbobenzoxy amino acid0,0'-dicarbobenzoxy-L-dopa benzyl esters The N-carbobenzoxyamino acidand 0,0'-dicarbobenzoxy-L-dopa benzyl ester hydrochloride were placed inmethylene chloride in a 3-necked round-bottomed flask fitted with adrying tube and mechanical stirring assembly and immersed in an icebath. Triethylamine (1 equivalent) added followed bydicyclohexylcarbodiimide (1 equivalent). Stirring continued at 0 for 1hour and 25 overnight. The reaction mixture was filtered, the filtrateevaporated to dryness, taken up in chloroform and extracted with 5% byweight aqueous NaHCO and 0.05 M

HCl. The chloroform layer was dried over MgSO filtered,

EXAMPLE 27 N-carbobenzoxyglycyl-0,0'-dicarbobenzoxy-L- i dopa benzylester .In the manner of Example 26, carbobenzoxyglycine (1.07 g., 5.1mm.) and 0,0-dicarbobenzoxy-L-dopa benzyl ester hydrochloride (3.0 g.,5.1 mm.) in methylene chloride (50 ml.)-dimethylformamide (1.4 ml.) wasreacted with triethylamine (516 mg., 5.1 mm.) anddicyclohexylcarbodiimide (1.07 g., 5.1 mm.). There was obtainedN-carbobenzoxyglycyl 0,0'-dicarbobenzoxy-L-dopa benzyl ester as acolorless oil.

EXAMPLE 28 N,O-dicarbobenzoxy-3-methoxy-L-tyrosyl-0,0-

dicarbobenzoxy-L-dopa benzyl ester In the manner of Example 26N,O-dicarbobenzoxy-3- methoxy-L-tyrosine (2.40 g., 5.0 mm.) and0,0'-dicarbobenzoxy-L-dopa benzyl ester hydrochloride (2.96 g., 5.0 mm.)in methylene chloride ml.) was reacted with triethylamine (507 mg., 5 .0mm.) and dicyclohexylcarboodiimide (1.05 g., 5.1 mm.). There wasobtained N, O dicarbobenzoxy-3-methoxy-L-tyrosyl-0',0'-dicarrbobenzoxy-L-dopa benzyl ester as a white crystalline productafter crystallization from ethyl acetate-ether, [c1 11.09 (c.=2.1percent, chloroform).

EXAMPLE 29 N,O-dicarbobenzoxy-L-tyrosy1-0,0'-dicarbobenzoxy-L-dopa-benzyl ester N,O-dicarbobenzoxy L-tyrosine (4.2 g.; 0.0094 mole)and 5.6 g. (0.0094- mole) of 0,0'-dicarbobenzoxy-L- dopa benzyl esterhydrochloride were coupled in the manner of Example 26 in 60 ml. ofmethylene chloride with 2.13 g. of dic'yclohexylcarbodiimide in thepresence of 1.33 ml. triethylamine as described earlier. Afterfiltration of the insoluble urea, the filtrate was washed with Water anddried over Na SO Evaporation of the solvent left a solid mass which wasrecrystallized from-ethyl acetate and petroleum ether to giveN,O-dicarbobenzoxy-L-tyrosyl-0,0'-dicarbobenzoxy-L-dopa benzyl estermelting at 120-123".

' EXAMPLE 30 N-carb obenzoxy-L-alanyl-O O'-dicarbobenzoxy- L-dopa benzylester Carbobenzoxy-L-alanine (5.6 g.; 0.025 mole) and 0, 0'dicarbobenzoxy-L-dopa benzyl ester hydrochloride (15 g., 0.25 mole) werecoupled in the manner of Example 26 in methylene chloride withdicyclohexylcarbodiimide (5.15 g., 0.025 mole) and 3.55 ml.triethylamine and worked up in the manner of Example 26 to give N-carbobenzoxy-L-alanyl 0,0 dicarbobenzoxy L dopa benzyl ester M.P.132-135 EXAMPLE 31 N-carbobenzoxy-L-leucyl-0,0'-dicarbobenzoxy-L- dopabenzyl ester 0,0 dicarbobenzoxy-L-dopa benzyl ester hydrochloride (8.88g., 0.015 mole) and carbobenzoxy-L-leucine (3.98 g., 0.015 mole) werecoupled in the manner of Example 26 in the presence ofdicyclohexylcarbodiimide (3.4 g.) and 2.12 ml. triethylamine in 70 ml.CH CI The reaction mixture was worked up in the manner of Exan tf ple 26to give N-carbobenzoxy-L-leucyl 0,0' dicarbo} benzoxy-L-dopa benzylester M.P. IDS-108.

EXAMPLE 32 I N,O,O-tricarbobenzoxy-D-dopa-O,0'-dicarbohenz ox'y-L-dopabenzyl ester 3 In the manner of Example 26, N,0,0'-tricarbobenzoxy-D-dopa (4.8 g., 8.0 mm.) and 0,0'-dicarbobenzoxy-L-dopa'benzyl ester hydrochloride (4.75 g., 810111111.) in methylenechloride (225 ml.) was reacted with triethylamine (804 mg,, 8.0 mm.) anddicyclohexylcarbodiimide (1.66 g., 8.05 mm.). After crystallization tromethyl ace tate-petroleum ether there was obtained N, Q,OI'-tricarbobenzoxy D-dopa-O,O'-dicarbobenzoxy L a dopa benzyl ester as white prismsM.P. 154-160".

EXAMPLE 33 N-carbobenzoxy-v-benzyl-L-glutamyl-0,0'-dicarbo Vbenzoxy-L-dopa benzyl ester In the manner of Example 31N-carbobenzoxyfl'menzyl-L-glutamate (3.72 g., mm.) and0,0=dicarbobenzoxy-L-dopa benzyl ester hydrochloride (5.92 g., 10 mm.)in methylene chloride" (75 ml.) was reacted with triethylamine (1.40ml., 10 mm.) and dicyclohexylcarbodiimide (2.06 g., 10 mm.). Thereaction product was N-carbobenzoxy-y-benzyl-L-glutamyl 0.0dicarbobe'nzoxy-L- dopa benzyl ester. This was white crystalline productafter crystallization from ethyl acetate-petroleum ether, [ch --10.70(c.=1 percent, methanol). I

24 EXAMPLE 34 General method for the preparation ofN,0,0'-tricarbobenzoxy-L-dopa-amino acid benzyl esters N,O,O'tricarbobenzoxy-L-dopa and the amino acid benzyl ester hydrochloridewere placed in methylene chloride in a 3-necked round-bottom flaskfitted with a mechanical stirring assembly and immersed in an ice-bath.Triethylamine (1 equivalent) added followed by dicyclo-vhexylbarbodiimide 1 equivalent). Stirring continued 'at' 0 for "1 hourand '25? overnight. The reaction mixture was filtered, the filtrateevaporated to dryness, taken up in chloroform andextracted with 5percent by weight aqueous NaHCO and 0.05 M HCl. The chloroform layer wasdried over MgSO filtered, evaporated to dryness and crystallized. 1

- EXAMPLE 35 N,0,0'-tricarbobenzoxy-L-dopa-glycine benzyl ester By theprocedure of Example 32 N,0,0-tricarbobenzoxy-L-dopa (7.44 g. 12.4 mm.)was reacted with glycine benzyl ester and hydrochloride (2.5 g., 12.4mm.) in methylene chloride (275 ml.) and dimethylformamide (12 ml.).Triethylamine (1.25 g., 12.4 mm.) and dicyclohexylcarbodiimide (2.6 g.,12.4 mm.) was added and the reaction mixture was evaporated to dryness,taken up in methylene chloride and worked up in the manner of Example32. N,0,0'-tricarbobenzoxy-L-dopa-glycine benzyl ester crystallized frommethylene chloridehexane as white prisms, M.P. -91.

EXAMPLE 36 N,0,0'-tricarbobenzoxy-L-dopa-3-methoxy-O-carbo-'benzoxy-L-tyrosine benzyl ester By the procedure of Example 32,N,0,0'-tricarbobenzoxy-L-dopa (3.18 g., 5.3 mm.) and3-methoxy-O-carbobenzoxy-L-tyrosine benzyl ester hydrochloride (2.50 g.,5.3 mm.) in methylene chloride ml.) was reacted with triethylamine (537mg., 5.3 mm.) and dicyclohexylcarbodiimide (1.135 g., 5.5 mm).N,0,0'-tricarbobenz- Oxy-L-dopa 3 methoxy-O-carbobenzoxy L tyrosinebenzyl ester crystallized from ethyl acetate-petroleum ether, M.P.156160.

EXAMPLE 37 N,0,0'-tricarbobenzoxy-L-dopa o-carbobenzoxy- L-tyrosinebenzyl ester :lhe protected dipeptidewas dissolved in glacial acetic acd: methanol, the catalyst (5 percent Pd on BaSOg), added and the mixturehydrogenated in a Parr apparatus at 35-50 p.s.i. The catalyst wasremoved by filtration through Celite and the filtrate evaporated todryness, evaporated from water and crystallized.

EXAMPLE 39 Glycyl-L-dopa By the procedure of Example 38,N-carbobenzoxyglycyl-0,0'-dicarbobenzoxy-L-dopa benzyl ester (25.6 g.,34.3 mm.) in 11:1 by volume mixtures of methanol: glacial acetic acid(240 ml.) was treated with 8.0 g. of 5 percent Pd-BaSQ; and hydrogenatedat 47.5 p.s.i. for 1,

hour. The mixture was filtered, evaporated to dryness, taken up inwater, evaporated and crystallized from waterisopropanol. There wasobtained glycyl-L-dopa as white prisms, M.P. 170-174", whichresolidified and melted .again 261-265 EXAMPLE 403-methoxy-Irtyrosyl-L-dopa 'By the procedure of Example 38,N,O-dicarbobenxoxy- 3-methoxy-L-tyrosyl-0,0'-dicarbobenzoxy-L-dopabenzyl .ester (2.85 g., 2.8 mm.) in methanolzglacial acetic acid:.tetrahydrofuran (50 ml.:5 ml.:30 ml.) was hydrogenated at 36.5 p.s.i.for 16 hours. The mixture was filtered, evaporated to dryness, taken upin water, evaporated and crystallized from water-isopropanol. There wasobtained 3- methoxy-L-tyrosyl-L-dopa as white prisms, M.P. 164- 166.

EXAMPLE 41 ,L-tyrosyl-L-dopa l L-alanyl-L-dopa Carbobenzoxy-Lalanyl0,0'-dicarbobenzoxy L dopa benzyl ester (9.6 g., 0.0126 mole) washydrogenated in a mixture of 100 ml. methanol, 100 ml. tetrahydrofuranand ml. acetic acid at 44 p.s.i. for 6 hours in the presence of 4 g. ofcatalyst. The reaction mixture was worked up in the manner of Example 38to give L-alanyl-L-dopa.

EXAMPLE 43 L-leucyl-L-dopa N carbobenzoxy-L-leucyl 0,0 dicarbobenzoxy-L-dopa benzyl ester (6.58 g., 0.0082 mole) was hydrogenated in the mannerof Example 38 with 2 g. of catalyst overnight at 47 p.s.i. The reactionmixture was worked up in the manner of Example 36 to produce L-leucyl-L-dopa which was dissolved in boiling isopropanol.

.Amorph'ous solid formed slowly on standing several days.

EXAMPLE 44 D-dopyl-L-dopa EXAMPLE 45 a-L-glutamyl-L-dopa carbobenzoxy7-benzyl-L-glutamyl-0,0'-dicarb0- benzoxy-L-dopa benzyl ester (6.05 g.,6.65 mm.) in methanol:acetic ,acidztetrahydorfuran (45 ml.:5 ml.:30 ml.)washydrogenated at 50 p.s.i. for 5 hours in the manner of Example 38.The mixture was filtered, evaporated todryness and evaporatedonce fromwater. The residue was taken up in water, extracted with ether andevaporated to dryness. The residue crystallized from water-ethanol.

There was obtained a-L-glutamyl-L-dopa as white crystalline product,M.P. 163-165 EXAMPLE 46 L-dopyl-glycineN,0,0-tricarbobenzoy-L-dopa-glycine benzyl ester (5.4 g., 7.22 mm.) inmethanol-acetic acid:tetrahydorfurane (50 ml:5 ml.: ml.) washydrogenated at 40 p.s.i. for 20 hours in the manner of Example 38, Themixture was filtered, evaporated to dryness, evaporated several timesfrom water and crystallized from water-isopropanol. There was obtainedL-dopyl-glycine as white prisms M.P. 159- 161, which resolidifies andmelts at 262-265 dec.

EXAMPLE 47 L-dopyl-3-methoxy-L-tyrosine N,0,0' tricarbobenzoxyL-dopa-3-methoxy-O-carbobenzoxy-L-tyrosine benzyl ester (3.0 g.,-2.95mm.) in methanolzacetic acidztetrahydrofuran (50ml.:5 ml.:50 ml.) washydrogenated at 35 p.s.i. for 16 hours in the manner described inconnection with Example 38. The mixture was filtered, evaporated todryness, evaporated several times from water and crystallized fromwater-isopropanol. There was obtained L-dopyl-3-methoxy-L- tyrosine as awhite solid, M.P. 164-167.

EXAMPLE 48 L-dopyl-L-tyrosine N,0,0' tricarbobenzoxyL-dopa-O-carbobenzoxy-L- tyrosine benzyl ester (5.5 g., 0.0056 mole) washydrogenated and worked up in the manner of Example 38 to give a solid.It was dissolved in a small amount of water and approximately 10 volumesof isopropanol was added. After standing several days L-dopyl-L-tyrosineof amorphous solid was obtained, M.P. 178180.

EXAMPLE 49 Preparation of N,0,0-tricarbobenzoxy-L-dopa Into a three neckround bottom flask fitted with mechanical stirrer and a nitrogen gasinlet tube was added 710.8 m1. of NNaOH and 1480 ml. water. The solutionwas chilled in an ice-salt bath and nitrogen gas bubbled for 30 minutes.L-Dopa g., 0.71 mole) was introduced and the solution was stirredvigorously while 404 g. of benzyloxycarbonylchloride (diluted to 2370ml. with ethyl ether) and 2370 ml. N NaOH were added simultaneously fromtwo separate dropping funnels under nitrogen during a period of 75minutes. After stirring an additional hour in the ice bath and two hoursat room temperature, the crystalline sodium salt formed. It wascollected by suction on coarse glass filter, washed thoroughly withether and then water to give a white solid mass. The solid was thenpartitioned between 2 1 each of methyl ether and 1 M citric acid. Theether layer was washed thoroughly with water, dried over ,Na SO andevaporated to give a clear oil. The compoundN,0,0'-tricarbobenzoyl-L-dopa was crystallized from a small volume of CHCl with petroleum ether (30-60 B.P.). M.P., 82-84. I

EXAMPLE 50 O,o' dicarbobenzoxy-L-dopa benzyl ester hydrochloride 7 Asolution of N,0,0-tricarbobenzoxy-L-dopa (230 g., 0.385 mole)in 5.3 l.of anhydrous diethyl ether was reacted with 97.4 g. (0.47 mole) ofphosphorus pentachloride. The clear solution obtained was evaporatedunder reduced pressure with exclusion of moisture. The residue obtainedwas evaporated once more with diethyl ether and again with ethyl acetateto give 0,0-dicarbobenzoxy-L-dopa-N-carboxy anhydride as a colorlesssyrup. This compound was immediately reacted with 690 ml. of N HCl inbenzyl alcohol at 50 C. for 30 minutes. As soon as the evolution of COgas was no longer evident, 15 volumes of dry diethyl ether were addedand the mixture allowed to stand overnight. The product formed wasrecrystallized from methanol with diethyl ether to give0,0-dicarbobenzoxy-L-dopa benzyl ester hydrochloride M.P. 114-117".

EXAMPLE 51 The reaction of Example 50 can also be carried outsatsifactorily with CHCl as solvent instead of diethyl ether. 'Thesolubility of the starting material seemed to be greater in CHCl thanethyl ether. Thus 5 g. (0.0083 mole) N,O, 'O' tricarbobenzoxy-L-dopa wasdissolved in 10 ml. of 'CHClg- Phosphorous pentachloride (2.1 g., 0.01mole) was added slowly with cooling. The mixture was then stirred atroom temperature for 30 min. until almost all of the PCl went intosolution. A small amount of insoluble material was filtered otf and thefiltrate was evaporated under reduced pressure (exclusion of moisture)to a heavy syrup. It was evaporated once more with fresh ether and againwith ethyl acetate. The oily residue was treated immediately with 15 ml.of freshly prepared N HCl in benzyl alcohol and stirred at 50 for 30minutes. Fifteen volumes of diethyl ether was added and the mixtureallowed to stand overnight after which a heavy solid formed.Recrystallization from methanol with diethyl ether gave0,0-dicarbobenzyloxy-L-dopa benzyl ester hydrochloride M.P. 108-111. TLcindicated that the prodnot was identical with that obtained above fromthe reaction carried out in anhydrous diethyl ether as in Example 49.

EXAMPLE 52 N,0,0'-tricarbobenzoxy-L-dopyl-0,0'-dicarbobenzoxy- L-dopabenzyl ester A solution containing 106 g. (0.178 mole) of0,0-dicarbobenzoxy-L-dopa benzyl ester hydrochloride in 400 ml. CHZCIQwas chilled in an ice bath and neutralized with 24.4 ml. oftriethylamiue. Some solid triethylammonium hydrochloride formed at thispoint. Without too much delay, 112 g. (0.178 mole) ofN,0,0'-tricarbobenzoxy-L-dopa dissolved in 400 ml. of chilled CH Cl wasadded followed by 39.2 g. (0.19 mole) of dicyclohexylcarbodiimide. Thereaction mixture Was stirred at for 1 hour and two hours at roomtemperature. The insoluble dicyclohexylurea and triethylammoniumhydrochloride were removed by suction filtration and washed severaltimes with small portions of CH Cl The conibined filtrate and washingswere washed with water, dried over Na SO and evaporated to dryness. Thecrude oil obtained was dissolved in a small volume of CH Cl and filteredto remove some more dicyclohexylurea. Evaporation of the filtrate underreduced pressure gave clear oil. This oil was crystallized from aminimum volume of CHQCI: with petroleum ether (B.P. 30-60) to giveN,(),O'-tricarbobenzoxy-L-dopa 0,0 dicarbobenzoxy- L-dopyl benzyl estermelting at 102-108.

EXAMPLE 53 L-dopyl-L-dopa -N,0,0'-tricarbobenzoxy-L-dopa-0,0dicarbobenzoxy- L-dopa benzyl ester (144 g., 0.127. mole) was dissolvedin a solvent mixture (800 ml.) containing peroxide free THF methanol andacetic acid in the ratio of 6:9:1 parts by volume. The catalyst (40 g.,percent Pd on BaSO was added and the mixture hydrogenated in a Parrapparatus at 45 p.s.i. for 5 hours. The catalyst was then removed'byfiltration and the filtrate evaporated to give a hard oil which ontreatment with 400 ml. abs. ethanol started to crystallize slowly (2-3days) giving crude didopa, M.P. 167-170". Recrystallization from hotethanol gave L-dopyl-L-dopa melting at 174-176".

In the manner of Example 26, carbobenzoxy-L-proline (1.28 g., 5.1 mm.)and 0,0'-dicarbobenzoxy-L-dopa ben- 28 zyl ester hydrochloride (3.0g.,-5.1 mm. in="methyle'ne chloride (50 ml.)-dimethylformamide (1 .4ml.)was-reacted with triethylamine (516 mg., 5.1 mm.) anddicyc'lohexylcarbodiimide 1.07 g., 5.1 mm). There was obtainedN-carbobenzoxy-L-prolyl-QO'-dicarbobenzoxy L dopa benzyl ester.

EXAMPLE 55 v N,N'-dicarbobenzoxy-L-lysyl-0,0'-dicarbobenzoxy-L- dopabenzyl ester By the procedure of Example 38, N-carbobenzoxy-L-prolyl-0,0'-dicarbobenzoxy-L dopa. benzyl ester is con verted toL-prolyl-L-dopa, white prisms, M.P. 170 C. dec.

EXAMPLE 57 L-lysyl-L-dopa By the procedure of Example 38,N,N-dicar'bobenzo xy L-lysyl-0,0-dicarbobenzoxy-L-dopa benzyl ester iscom verted to L-lysyl-L-dopa.

:EXAMPLE 58 L-pyroglutamyl-0,0'-dicarbobenzoxy-L-dopa benzyl ester Inthe manner of Example 26, L-pyroglutamic acid and0,0'-dicarbobenzoxy-L-dopa benzyl ester hydrochloride, were reacted toproduce L-pyroglutamyl-QO' dicarbobenzoxy-L-dopa benzyl ester as whiteprisms, M.P. 133 to 136 C. 5

EXAMPLE 59 L-pyroglutamylwL-dopa By the procedure of Example 3'8,L-pyroglutamyl- 0,0'-dicarbobenzoxyy- L -.dopa benzyl ester washydrogenated to produce L-pyroglutamyl-L-dopaas white powder, M.P. C.dec. i 1

EXAMPLE 60 N-carbobenzoxy-L-seryl-0,0'-dicarbobenzoxy-i di p 5 benzylester 7 i N-carbobenzoxy-L-serine (2.40 g-., 0.01 ole)-and-'O,O'-dicarbobenzoxy L dopa benzyl ester hydrochloride were dissolved inmethylene chloride (50 ml.) and placed in a 250 ml. B-necked roundbottomed flask fitted with a magnetic stirrer and immersed in, anice-saltbath..:-Triethylarnine (1.40 cc., 0.01' mole) was addedfollowed-by dicyclohexylcarbodiimide (2.06 g., 0.01, mole). Stirringcontinued at 0 C. for 2 hours and2 5 C. overnight. The reaction mixturewas filtered and the filtrate extracted with an aqueous solutioncontaining. 5% byv weight o f NaHCO and 1 M aqueous citric acid, driedOver MgSQL filtered, evaporated to dryness and crystallized ,froin Qihylacetate-petroleum ether. There was. obtained. N-carho benzoxy-L-seryl-OU-dicarbobenzoxy L dopa benzyl ester as white prisms, M.P. ISO-153 C. 1

EXAMPLE 61 N-carbobenzoxy-L-valyl-QO' dicarbobenzoxy-L-dopa benzyl esterN-carbobenzoxy-Lvaline (2.52 g., 0.0 1" 111615 "and 0,O'-dicarbobenzoxy-L dopa "benzyl 'ester mwmemeuae (5.92 g., 0.01 mole)were dissolved in methylene'chloride EXAMPLE 62 v N-t-butyloxycarbonyla-benzyl-L-glutamyl-QO'-di-.

carbobenzoxy-L-dopa benzyl esterN-t-butyloxycarbonyl-a-benzyl-L-glutamate (3.37 g., 0.01 mole) and0,0-dicarbobenzoxy-L-dopa benzyl ester hydrochloride (5.92 g., 0.01mole) were placed in a sys tem described in Example 60. The reactionmixture was cooled to C. and triethylamine (1.40 cc., 0.01 mole) addedfollowed by dicyclohexylcarbodiimide (2.05 g., "0.01 mole) and stirredat 0 C. for 2 hours and 25 C. overnight. The reaction mixture'wasfiltered, extracted with an aqueous solution containing by weight NaHCOand l M aqueous citric acid, dried over MgSO filtered and evaporated todryness. The residue was crystallized from ethyl acetate-petroleum etherand produced N-t-butyloxycarbonyl-a-benzyl-L-glutamyl 0,0dicarbobenzoxy-L-dopa benzyl ester as white crystalline product, M.P. 8285.5 C.

EXAMPLE 63 1 N,0,0'-tricarbobenzoxy-L-dopa (12.0 g., 0.02 mole) andN-carbobenzoxy-L-lysine t-butyl ester hydrochloride (7.50 g., 0.02 mole)were placed in the system set forth in Example 60. The mixture wascooled to 0 C. and triethylamine (2.80 cc., 0.02 mole) was addedfollowed by dicyclohexylcarbodiimide (4.12 g., 0.02 mole) and stirred at0 C. for one hour and 25 C. overnight. The reaction mixture was workedup in the manner described in Example 60, and the product crystallizedfrom ethyl acetate-petroleum ether. There was obtainedN,0,0'-tricarbobenzoxy L-dopyl-N -carbobenzoxy-L-lysine-t-butyl ester aswhite prisms, M.P. 87.5-90.5 C.

EXAMPLE 64 L-seryl-L-dopa By the procedure of Example 38,N-carbobenzoxy-L- seryl-0,0'-dicarbobenzoxy-L-dopa benzyl ester (5.2 g.,6.70 mmole) in tetrahydrofuranzglaeial acetic acidzmethanol (20 ml.:20ml.:20 ml.) was hydrogenated at 45 p.s.i. for 6 hours using 3.0 g. of 5%Pd-BaSO as catalyst and the reaction crystallized fromwater-isopropanol. There was obtained L-seryl-L-doda as white prisms,M.P. 149 C.

EXAMPLE 65 L-valyl-L-dopa By the procedure of Example 38,N-carbobenzoxy-L- 'valyl-0,0'-dicarbobenzoxy-L-dopa benzyl ester (5.7g., 7.23 mmole) in tetrahydrofuranzacetic acidzrnethanol (20 'ml'.:20ml.:50 ml.) was hydrogenated at 45 p.s.i. for 5 hours using 3.5 g. of 5%Pd-BaSO The product was crystallized from ethanol-Water. There wasobtained L- valyl-L-dopa as white prisms, M.P. 156 C.

EXAMPLE 66 L-'y-glutamyl-L-dopa The protected dipeptide N tbutyloxycarbonyl-abenzyl-L-glutamyl-QO' dicarbobenzoxy-L-dopa benzylester (4.1 g., 4.69 mmole) in methanol:acetic acid (50 ml.:10 ml.) washydrogenated at 48 p.s.i. for 5 /2 hours using 4.2 g. of 5% Pd-BaSO andwas worked in the manner of Example 38. The residue was triturated withdiethyl ether and treated with a solution of trifiuoroaceticacidzmethylene chloride (25 ml.:25 ml.) and stirred at 25 C..for 30minutes. It was evaporated to dryness and the residue evaporated severaltimes from water, taken up in ethanoland triethylamine added to pH 7.The re- 30 sultant precipitate was filtered, washed with ethanol andcrystallized from ethanol-water. There was obtained L- 6-glutamyl-L-dopaas a white amorphous solid.

' EXAMPLE 67 I L-dopyl-L-lysine trifluoroacetate The dipeptideN,0,0'-tricarbobenzoxy-L-dopyl- '-carbobenzOxy-L-lysine-t-butyl ester(7.6 g., 8.28 mmole) in methanolzacetic' acid (125 ml.:10 ml.) washydrogenated at' 50 p.s.i. for 48 hours using 5.0 g. of 5% Pd-BaSO; andworked up in the manner of Example 38. The residue was crystallized fromethanol to give 4.1 g. of intermediate, L-dopyl-L-lysine t-butyl ester.A solution of 2.0 g. of the intermediate was reacted withtrifiuoroacetic acid: methylene chloride (40 ml.:40 ml.) and stirred at25 C. for 2' A-hours. It was evaporated to dryness, taken up in methanoland precipitated with isopropanol. There was obtained -L-dopyl-L-lysinetrifluoroacetate as a white solid.

EXAMPLE 68 L-prolyl-L-dopa-L-dopa Twenty-five ml. of dirnethylformamidewas chilled in an ice-bath and bubbled with nitrogen for 15 minuteswhile L-dopa-L-dopa (1.8 g., 4.8 mm.) was added. After the soliddissolved, 1.8 g. (4.9 mm.) of N-carbobenzoxy- L-proline p-nitrophenylester was added followed by 0.68 ml. of triethylamine. The mixture wasstirred at 0 C. for 2 hours and 22 hours at room temperature. Thereaction mixture was then acidified with 1 ml. of acetic acid and thesolvent removed by evaporation under reduced pressure. The residual paleyellowish oil was triturated with diethyl ether and precipitated from asmall volume of methanol with diethyl ether to give 2.1 g. of crudepartially protected tripeptide. A portion of this material (1.2 g.) wasstirred overnight in a mixture of 50 ml. each of water and methylenechloride under nitrogen and the water layer was lyophilized to give 0.8g. of white powder. It was dissolved in 30 ml. of solvent mixture(methanolzwaterzacetic acid; 10:10:1) and hydrogenated overnight at 50p.s.i. with 0.35 g. of 5% *Pd on BaSO as catalyst. The catalyst wasremoved by filtration and the filtrate evaporated to a slightly coloredoil which on treatment with 40 ml. of methanol gave crystalline solid(0.55 g.). It was then recrystallized from hot water and isopropanol togive L-pyrolyl-L-dopa-L-dopa, M.'P. 260- 261 C.

EXAMPLE 69 L-3- (3, 4-dihydroxyphenyl) alanylglycylglycine Into a 250m1. l-necked round bottomed flask fitted with a magnetic stirrer wasplaced N,0,0'-tricarbobenzoxy-L-dopa-p-nitrophenyl ester (5.05 g., 7.0mmoles) and glycylglycine hydrochloride monohydrate (1.24 g., 6.66mmoles). There was added 50 ml. dimethylformamide (dried over molecularsieve Linde Type 4A, 4-8 mesh). The insoluble reaction mixture waschilled at 0 for 20 minutes and triethylamine (1.35 g., 13.3 mmoles) wasadded. The yellow mixture was stirred at 0 C. for 2 hours at 25 C. forhours.

The reaction mixture was filtered, treated with 1.5 ml. glacial aceticacid and the solution was evaporated in vacuo at 35 to remove thedimethylformamide. The residual oil was triturated with anhydrous ethylether (five times), .dissolved in warm ethyl acetate, chilled andremoved some salt by filtration. The filtrate was evaporated to drynessand the residual oil was dissolved in aqueous solution containing 5% byweight sodium bicarbonate and washed with ethyl ether. The aqueous phasewas slowly acidified with 1 M aqueous hydrochloric acid to afford anoff-white gummy precipitate which was dissolved in-ethyl acetate andwashed with saturated sodium chloride. It was dried over MgSO filteredand evapmated to dryness to alford N,0,0 -trisbenzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)alanylglycylglycine as a paleyellow amorphoussolid.

A solution of 3.7 g. of this solid in 140 ml. of 10% by volume aceticacid in methanol was placed into a 500 ml. pressure bottle. There wasadded 0.8 g. of 5% by weight palladium on 95% by weight barium sulfateand the mixture was hydrogenated for 5 /2 hours at an initial pressureof 41 p.s.i. The mixture was filtered over a methanol moistened pad ofCelite and the filtrate evaporated to dryness. The residual oil wasdissolved in distilled water which was pre-treated with argon for 20minutes, filtered and evaporated to dryness. This process was repeatedtwice and the residual oil was dissolved in a minimum of the argontreated water and an excess of isopropanol was added slowly. It wasallowed to stand for 2 hours and a colorless solution (B) was decantedfrom a violet oil (A). Solution B was chilled at overnight to afford awhite crystalline precipitate which was collected by filtration andwashed with 20% by volume water in 80% by volume of isopropanol andisopropanol. It was dried in vacuo to afford L-3-(3,4-dihydroxyphenyl)alanylglycylglycine as white crystals, M.P. ISO-182 C.

In order to obtain additional amounts of product, the violet oil (A) wastreated with a small volume of the argon treated water and a whitecrystalline solid precipitated. The solid was collected by filtrationand washed with 20% by volume of water in isopropanol, isopropanol andanhydrous ethyl ether. The product was dried in vacuo to affordL-3-(3,4-dihydroxyphenyl)alanylglycylglycine as a white crystallinesolid, M.P. 1-86188 C.

EXAMPLE 70 Glycyl-L-3-(3,4-dihydroxyphenyl)alanylglycine Into a 250 ml.l-necked round bottomed flask, fitted with a magnetic stirrer was placedL-3-(3,4 dihydroxyphenyl)alanylglycine (3.0 g., 11.8 mmoles) and 120 ml.dimethylfor-mamide was added. To this insoluble mixture was addedN-carbobenzoxyglycine p-nitrophenyl ester (3.98 g., 12.0 mmoles) and thereaction mixture was chilled in ice for 20 minutes and treated withtriethylamine (1.195 g., 11.8 mmoles). The solution turned yellow andmost of the solids dissolved, stirring continued at 0 C. for 2 hours andat 25 C. for 20 hours to give a clear yellow solution.

At the end of this time 1.5 ml. of glacial acetic acid was added and thesolution was evaporated in vacuo at 35 C. to remove thedimethylformamide. The residual oil was triturated with anhydrous ethylether (three times). The oil was dissolved in methanol, precipitatedslowly with anhydrous ethyl ether, decanted and the precipitated oil wasdissolved in boiling absolute ethanol "(about 200 ml.). It was filteredby gravity and chilled at 0 C. overnight. Some starting dipeptide wasremoved by filtration and the filtrate was combined with the firstmethanol diethyl ether filtrate and evaporated to dryness. The residualoil was treated with ethyl acetate. There was obtained 1.4 g. of a whiteamorphous precipitate of dipeptide starting material. The mother liquorwas evaporated to dryness and the residual oil dissolved in aqueous 5%by weight sodium bicarbonate and washed with ethyl acetate. The aqueouslayer was treated with a trace of sodium hydrosulfite to preventoxidation and filtration. It was washed twice with ethyl acetate andacidified with 1 M aqueous hydrochloric acid and extracted into ethylacetate (three times). The combined ethyl acetate extract was dried'overM-gSO filtered and evaporated to dryness to affordN-carbobenzoxy-glycyl-L-3-(3,4-dihydroxyphenyl)alanylglycine as an oil.

A solution of 1.3 g. of this oil in 50 ml. of by volume acetic acid in90% by volume methanol was placed into a 250 ml. pressure" bottle. Therewas added 0.7 g. of 5% by weight palladium on 95% by weight bariumsulfate and the mixture was hydrogenated for 4 hours at an initialpressure of 50 p.s.i. The mixture was filtered over a methanol moistenedpad of Celite (diatomaceous earth) and the filtrate evaporated todryness. The yellow residual oil was dissolved indistilled water whichwas pre-treated with argon for 20 minutes. It was washed with ethylacetate (two times) and ethyl ether and evaporated to dryness. Theresidual oil was dissolved in a minimum volume of the argon treatedwater, filtered and treated with isopropanol until cloudy. It waschilled at 0 C. overnight and the precipitate was collected byfiltration, washed with 20% by volume water by volume isopropanol,isopropanol and ethyl ether and dried in vacuo to affordglycyl-L-3-(3,4-dihydroxyphenyl)alanylglycine as white crystals, M.P.217-220 C.

EXAMPLE 71 Glycyl-glycyl-L-B- 3,4-dihydroxyphenyl) alanine(Gly-Gly-L-dopa) Into a 250 ml. l-necked round bottom flask fitted witha magnetic stirrer was placed glycyl-L-3-(3,4-dihydroxyphenyl)alanine(3.0 g., 11.8 mmoles) and N-carbobenzoxyglycine p-nitrophenyl ester(3.98 g., 12.0 mmoles). There was added 50 ml. dimethylformamide and thesolution was chilled in ice for 20 minutes and triethylamine (1.195 g.,11.8 mmoles) wasadded. The solution turned yellow and most of the solidsdissolved. Stirring continued at 0 C. for 2 hours and 25 C. for hours.

There was added 1.5 ml. glacial acetic acid and the solution wasevaporated in vacuo at 35 C. to remove the dimethylforrnamide. Theresidual oil was triturated with anhydrous ethyl ether (five times). Theoil was dissolved in an aqueous solution containing 5% by weight sodiumbicarbonate, washed with ethyl ether (two' times), acidified with 1 Mhydrochloric acid and extracted with ethyl acetate (two times). Thecombined ethyl acetate extract was evaporated to formN-carbobenzoxyglycyl-glycyl-lrli- (3,4-dihydroxyphenyl)alanine as ayellow oil.

A solution of this yellow oil in ml. of 10% by volume acetic acid in 90%by volume methanol was placed into a 500 ml. pressure bottle. Therewasadded 1.2 g. of 5% by weight palladium on 95% by weight bariumsulfate, and the mixture was hydrogenated for 16 hours at an initialpressure of 42 p.s.i. The product was insoluble in the solvent mixture.The reaction mixture was dissolved on addition of distilled water whichwas pre-treated with argon for 20 minutes. The mixture was filtered overa methanol moistened pad of Celite and the filtrate evaporated todryness. The residual oil was dissolved in the argon treated water,filtered and evaporated to dryness. The evaporation was repeated 2 moretimes and the residual oil was dissolved in a minimum volume of theargon treated water, isopropanol was added until cloudy, and the violetsolution was chilled at 0 C. The resultant gelatinous precipitate wascollected by filtration, dissolved in warm argon treated water andisopropanol added to the cloud point. It was filtered to remove somegray impurities, more isopropanol added and chilled at 0 C. overnight.The resultant gelatinous precipitate was col-lected by filtration, andwashed with isopropanol and anhydrous ethyl ether. It was dried in vacuoto afford glycyl-glycyl-L-3-(3,4-dihydroxyphenyl) alanine(Gly-Gly-L-dopa), M.P. -l72 C.

EXAMPLE 72 N,0,0'-tricarbobenzoxy-L-dopa p-nitrophenyl ester A solutionof N,0,0'-tricarbobenzoxy-L-dopa prepared in Example 5 (81.3 g., 0.136mole) in 700 ml. CH Cl was reacted with 22.35 g. (0.16 mole) ofp-nitrophenol in the presence of 33.2 g. (0.162 mole) dicyclohexylcarbodiimide at 0 C. for 21 hours. The insoluble dicyclohexylurea formedwas filtered oil and the filtrate was evaporated to give 116 g. ofslightly yellowish oil; On treatment with small amount of ethanol, itbecame a solid mass. The product was dissolved in CHQC]: and filteredthrough a 10 cm. layer of fiuorosil to remove some impurities. Thefiltrate was evaporated and treated with ethanol to giveN,0,0-tricarbobenzoxy-L-dopa p-nitrophenyl ester as crystalline product,M.P. 1155- 1 17 C.

33.; E AMB E 73 L-dopyL'L-dopyl-L-dopa Fifty m1. of DMEWas bubbled withnitrogen gas at for 15 minutes. L-dopa-Lvdopa (4.17 g., 0.011 mole) wereadded followed by 8.8 g. (0.012 mole) of N,0,0'-tricarbobenzoxy-L-dopap-nitrophenyl ester and 1.71 ml. triethylamine. The reaction mixture wasstirred at 0 C. for an of 10:1:1' parts by volume with 2.7' g'. ofcatalyst by weight Pd on a95% by weight 'BaSO at 45 p.s.i. for

24 hours. The catalyst was removed by' filtration tinder nitrogen andthe filtrate evaporated to a heavy'syrup.

Upon treatment with 500 ml. peroxide free THF" L-dopa L-dopa-L-dopa wasobtained as'a slightly pinkish white powder. Reprecipitation of thismaterial from -30 ml. methanol with 700 ml. peroxide free THF gave L'-dopyl- L-dopyl-L-dopa as a white amorphous solid.=

EXAMPLE 74 N,0,0'-tricarbobenzoxy-L-dopa-dibenzyl-L-glutamateN,0,0'-tricarbobenzoxy-L-dopa (6.0 g., 0.010 mole) anddibenzyl-L-glutamate hydrochloride (3.64 g., 0.01 mole) were coupled bythe procedure of Example 32 in the presence of 2.06 g. ofdicyclohexylcarbodiimide and 1.40 ml. triethylamine in 75 ml. ofmethylene chloride. The reaction mixture was worked up by the procedureof Example 32 to giveN,0,0'-tricarbobenzoxy-L-dopa-dibenzyl-L-glutamate, M.P. l15.5118 C.

- ""QEXAMPLE 75 L -dO a-IrgIutamic acid N,0,0'tricarbobenzoxy-L-dopa-dibenzyl-L-glutamate (4.9 g., 5.39 mm.) inmetli'ariolzacetic acid:tetrahydrofuran (75 ml.:5 ml.':25 ml.)wa's"hydrogenated at 48 p.s.i. for 20 hours in the manner of Example 38.The mixture was filtered, evaporated to dryness and crystallized fromwater-isopropanol. There was obtained L-dopa- L-glutamic acid as whiteprisms, M.P.' 157-159 C.

7 EXAMPLE 76 Tablets are manufactured utilizingthefollowing comri isi Hj/ Glycyl-glycyl-L-S-(3,4-dihydroxyphenyl)alanine 100 Lactose 61 Cornstarch a j 30 y iny py ol dq e j- 4 The active substance is mixed withthe lactose and the corn starch, and, after the addition of a solutionoipoly: vinylpyrrolidone in v40 ml. ofethanOL: g nulated. The granulateis dried at 30 C., mixed with talcum and pressed to tablets s-Individualweight of one tablet 200 Active substance content of onetablet 100 EXAMPLE. 71

Gelatin capsules are manufactured utiliaing the following composition: 1

bdopyl-L-dopyl-L-dopa 50.0 Mannitol 98.5 Stearic' acid 1.5.

The ingredients are homogeneously mixed and filled into interlockinggelatin 5 Individual weight of one capsule 150 Active substance contentof one capsule 50 I claim z 1. A compound selected from the compounds ofthe 10 formulae:

J v A, V i

o 0 NHrcH 'NH- :H ii 1 rrrcH-co0H- 1 R CH| 0 0 NHPCHiL -NHCHiJ-NHCH-C00H wherein R and R' are OR; -cH, OH; cm+@ OH or the source-"ofvariation-in structure of the a-side chain which differentiates onenatural protein occurring a-amino acid from another; R and R are or thesource of variation in structure of the a-side chain whichdifferentiates one natural protein occurring a-amino acid from another;and R is lower alkyl; or pharmaceutically acceptable salts thereof.

2. The compound of claim 1 wherein said compound has the formula:

I 1: it

wherein R and R are as above;

or pharmaceutically acceptable salts thereof.

' 3. The compound of claim 2 wherein said compound is L 3-- (3,4dihydroxyphenyl) alanyl L-(3,4-dihy- 75droxyphenyl-alanyl-L-(3,4-dihydroxyphenyl)-alanine.

capsules via a capsule filling hee-120': v 35" 36 '4; camieiisa"of-claim --'whrei;1 saiaeqms ofinii is 13. The compound bf 'laim' iz'v'v'uerein R is Ii dopyl glycy'l glycine.

S The compound of claim 1 wherein said compound has the formula:

and; R is as-above.

wherein R and R are as above; r 15 h cbmpmindiofi c-ompqmdi orpharmaceutically acceptable salts thereof. wl r rh qem '--I 6. Thecompound of claim 5 wherein said compound is 111K111? commend i slamWher ul S s rc L-propyl-L-dopyl-L-dopa. f variation inflt s r i s hersidec a h ch."

7. Th com and of claim 6 wherein sa d com und is er tiat s. onefiilturalP f acid P i lycyl-zli'cvl-L ona. K 90 18, Thewmnou d-ofclaim 11wherein-s comp unds v f- 1', I l O V d i L d y ..v y M 8 The w c wheremcompmm 1S 19.-. The'cqmpound of; claim l'lwherem-saidcompoungt.

rmulai;

wherein R; and R are as above; or pharmaceutically acceptable saltsthereof.

9. The compound of claim 1 wherein said compound is y 1 rglycidyl-L-dopyhglycinc. V 1 v 10. Acompound of the formula: I a ,3

wherein R is lower alkyl; R is" a conventional amino 1| 40 protectinggroup removable hyhydrolysis or hydro- NHr-( JH-O-NH-OHQ genolysis; R islower alkyl, or ar yl lower alkyl; R is CH: CH: I l V v i I i l I 0R; A

or pharmaceutically accpetable "acid addition salts thereof.

11. The compound of claim 10 wherein said compound is L-3(3,4dihydroxyphe'nylI-N-(3,4-dihydroxypheneth- YD -alaninamide. Y 1

mike sour s Wish? in tm wis Q 1 aside chain between difierent naturalprotein occurring' gzt amino acids wherein all free amino andcarboxyi'g'roups" m p i'tic lf P! 5 Y b y. 9". o lys s or t s nq s u ad, whe e? the icks g l a swan my l s. f ee a e ss ri bi' a r w Wom lNHFCH- a: t c thereto hy hydrolysis or hydrogenolysis; and R flare H12Y": I hydrogen or 'a group convertible an by hydrov genolysis'orhydrolysis; R i 'hydrogen'ofa rq I convertible theretoby'hydrogenolysis'f or' pharmaceutically acceptablesaltsthereof.

4 12.,An L-L-antipodecof a compound of the iorniula:

OH" 24. The compound'of claim-23 wherein-Ede;

H I p 0R0 wherein R is v 42H: i

OH H F.

| and R is as ahoue. I f --C rm@ 25. The compound of claim 24 wherein Ris arylalk- OH o ycarbony c,

a r v 26. The compound of claim 25 whereinzsaidcompound or the source ofvariation in structure of the aside chain isN-benzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)-alanwhich differentiatesone natural protein occurring yl-L-3-(3,4-dihydroxyphenyl)-alaninebenzyl ester.

u-amino acid from another; and R is lowervalkyl; 27. Thecompoundof claim24 wherein said com-' or pharmaceutically acceptable salts thereof. 1pound is N,0,0-tris-benzyloxycarbonyl-L-3-(3,4-dihy- B: drag and R and Rare as above.

29. The compound of claim 28 wherein said compound isN,0,0'-tris-benzyloxycarbonyl L-dopyl-3-methoxy-O-carbobenzoxy-L-tyrosine benzyl ester.

30. The compound of claim 23 wherein R' is said source of variation instructure of the u-side chain between diiferent natural a-amino acidswherein all the free amino and carboxyl groups are protected by a groupconvertible thereto by hydrolysis or hydrogenolysis.

31. The compound of claim 30 wherein R and R are carbobenzoxy. d v

32. The compound of claim 30; wherein said compound isN,0,0-tricarbobenzbxy-Ldopyl-glycine benzyl ester.

33. The compound of claim 30 wherein said compound isN,0,0tricarbobenzoXy-L dopyl-O-carbobenzoxy-L- tyrosine benzyl ester.

34. The compound of the formula:

wherein R is a conventional amino protecting group removable byhydrogenolysis or hydrolysis; R is hy' drogen or a group convertiblethereto by hydrolysis or hydrogenolysis; R is lower alkyl'or aryl loweralkyl; R is the source of variation in structure .of the aside chainbetween difierent natural protein occurring a-amino acids wherein allfree amino and earboxy groups are protected, by a group. convertible,thereto by hydrolysis or hydrogenolysis and where hydroxy groups may befree or protected bya group convertibl thereto by hydrolysis orhydrogenolysis, and I R is lower alkyl and R is.hydroxy orra groupconvertible thereto by hydrogenolysis,

or pharmaeeutically acceptable salts thereof.

35. The compound of claim 34 wherein R is and R and R are as above.

36. The compound of claim 35 wherein said compound is N,Odicarbobenzoxy-3-met.hoxy-L-tyrosyl-0,0-dicarbobenzoxy-L-dopa benzylester. g

37. The compound of claim 34 wherein R is said source of variation instructure of the u-side. chain be- 41. The compound of claim 38-whereinsaid compound is N carbobenzoxy-'y-beniyl-L-glutamyl-0,0 dicar-bo'benzoxy-L-dopa benzyl ester.

42. A compound of'the foi'mula'z" ny-NH- m-ooorr wherein R isaralkoxycarbonyl; R is hydrogen or aralkyloxycarbonyl.

45. The compound of claim 44 wherein said compound isN-benzyloxycarbonyl-L-3-(3,4-dihydroxyphenyl)-alanine'. I p

46. The compound of'cl aim 44 wherein said coin-1 pound isN-benzyloxycarbonyl-L'3-(3,4 dihydroxyph n-f yl)-alanine. ,1

47. A compound of the formula:

whereinR is hydrogen or groupconvertible thereto by hydrolysis; R 'is'1o'wer alkyl? Rq' i'sfhydrogeh or lower alkyl; R and R are hydrogen oragroup convertible thereto by.,hydrolysis; R is :orthe source ofvariation'in structure of the or-s'ide chain between different naturalprotein" occurring 'a-aminb acids-wherein a11- hydroxyg airline-groupsare free-or protected by a "group convertible theretobyhydrolysis-"vvithth"proviso that one of R R R and R is other thanhydrogeni or -pharmaceutically acceptablesalts "thereof; said com poundhaving- 'a'f'ree 'carboxy. or free'amino-groupi 3a 48. The compound ofthe formula:

OR" wherein R is hydrogen or lower alkyl; R is hydrogen or a groupconvertible thereto by hydrolysis; R is lower alkyl; R is hydrogen orlower alkyl; R is hy drogen or a group convertible thereto byhydrolysis;

' or the source of variation in structure of the a-side chain betweendifferent natural essential a-arnino acids wherein all amino, carboxyand hydroxy groups are free or protected by a group removable byhydrolysis with the proviso that one of R R and R is other thanhydrogen: 7 or pharmaceutically acceptable salts thereof, said compoundhaving a free carboxy or free amino group.

49. A compound of the formula:

Ra a

wherein R and R are hydrogen or a group convertible thereto 'byhydrolysis with one of R and R being other than hydrogen;

50. A compound of the. formula:

Rt 7 wherein R is lower alkyl; R is hydrogen or an amino protectinggroup which can be removed by hydrolysis or .hydrogenolysis; R5 ishydrogen or a group convertible thereto b y hydrolysis; R is hydrogen,lower alkyl or aryl lower alkyl; R and R are a on. R1 -om@ -oH, on OR orthe source of variation in structure of the u-side i 51. The compound ofclaim 50 wherein said compound isN,O,0'-tricarbobenzoxy-L-dopyl-L-dopyl-L-dopa.

52. The compound of claim 50 wherein said compound isN,O',O'-trisbenzyloxycarbonyl L 3(3,4-dihydroxyphenyl-alanyl-glycyl-glycine.

chain between difierent natural protein occurring a- 53. A compound ofthe formula:

II 0 R5 NH;CHO-NH-YJH-Ql-NH-CH-C 0 0 R11 l Baa Baa H2 wherein R is loweralkyl; R is hydrogen or an amino protecting group which can be removedby hydrogenolysis or hydrolysis; R is hydrogen or a group convertiblethereto by hydrolysis or hydrogenolysis; R is hydro gen, lower alkyl oraryl lower alkyl; R is 0 Re 0 R: --CH: CH1 URI or the source ofvariation in structure of the a-side chain between different naturalprotein occurring oramino acids wherein all free amino acid carboxygroups are protected by a group convertible thereto by hydrolysis orhydrogenolysis and where hydroxy groups may be free or protected by agroup convertible thereto by hydrolysis or hydrogenolysis; R is hydrogenor a group convertible thereto by hydrogenolysis; R is or the source ofvariation in structure of the a-side chain 'between different naturalprotein occurring atamino acids wherein all free amino and carboxygroups are protected by a. group convertible thereto by hydrolysis orhydrogenolysis and where the hydroxy groups may be free or protected bya group convertible thereto by hydrolysis or hydrogenolysis;

or pharmaceutically acceptable salts thereof with the proviso that thecompound has at least one protected amino, carboxy or hydroxy group.

54. The compound of claim 53 wherein said compound is Ncarbobenzoxyglycyl-glycyl-L-3-(3,4dihydroxypheny1)-alanine.

55. A compound of the formula:

wherein R is lower alkyl; R is hydrogen or an amino protecting groupwhich can be removed by hydrolysis or hydrogenolysis; R is hydrogen,lower alkyl or aryl 7 lower alkoxy; R and R are or the source ofvariation between different natural pro I tein occurring a-amino acidswherein all free amino and carboxy groups are protected by a groupconvertible thereto by hydrolysis or hydrogenolysis and where the

